Java语言程序设计(基础篇)原书第十版 梁勇著 第一章答案

梁勇java第十版复习题答案1. 简述Java中接口和抽象类的区别。

接口是一种完全抽象的类，可以包含抽象方法和默认方法，不能包含实现细节，而抽象类可以包含抽象方法和具体方法，可以包含成员变量和方法实现。

2. 描述Java中多态的实现机制。

多态的实现依赖于方法的重载和重写。

重载是指在同一个类中定义多个同名方法，但参数列表不同；重写是指子类中定义一个与父类同名的方法，并且参数列表相同。

3. 如何在Java中实现单例模式？单例模式可以通过私有构造函数、私有静态实例和公有静态方法来实现。

私有构造函数防止外部实例化，私有静态实例确保只创建一个对象，公有静态方法提供全局访问点。

4. 解释Java中的垃圾回收机制。

垃圾回收是Java自动管理内存的一种机制，它通过识别不再使用的对象并释放其占用的内存空间来防止内存泄漏。

垃圾回收器会定期执行，但具体的执行时机和方式由JVM控制。

5. 描述Java中异常处理的流程。

异常处理包括try、catch和finally块。

try块中放置可能抛出异常的代码，catch块捕获并处理异常，finally块中的代码无论是否发生异常都会执行，常用于资源清理。

6. 简述Java集合框架中的List、Set和Map的区别。

List是一个有序集合，允许重复元素；Set是一个无序集合，不允许重复元素；Map是一个键值对集合，键不允许重复，值可以重复。

7. 如何在Java中实现线程同步？线程同步可以通过synchronized关键字、Lock接口和volatile关键字来实现。

synchronized关键字可以修饰方法或代码块，保证同一时间只有一个线程访问；Lock接口提供了更灵活的锁定机制；volatile关键字确保变量的可见性和有序性。

8. 描述Java中泛型的作用。

泛型提供了一种类型安全的方式，允许在编译时检查类型错误，避免了类型转换的麻烦，并提高了代码的重用性。

9. 简述Java中I/O流的分类。

第一章1.1public class Test{public static void main(String[]args){System.out.println("Welcome to Java!"); System.out.println("Welcome to Computer Science!");System.out.println("Progr amming is fun.");}}1.2public class Test{public static void main(String[]args){for(int i=0;i<=4;i++){System.out.println("Welcome to Java!");}}}1.3public class Test{public static void main(String[]args){System.out.println("]");System.out.printl n("]");System.out.println("]]");System.out.println("]]");}}public class Test{public static void main(String[]args){System.out.println("A"); System.out.println("A A");System.out.println("AAAAA");System.out.println("A A");}}public class Test{public static void main(String[]args){System.out.println("V V");System.out.println("V V");System.out.println("V V");System.out.println(" V");}}1.4public class Test{public static void main(String[]args){System.out.println("a a^2a^3");System.out.println("111");System.out.println("248");System.out.println("3 927");System.out.println("41664");}}1.5public class Test{public static void main(String[]args){System.out.println((9.5*4.5-2.5*3)/(45.5-3.5) );}}1.6public class Test{public static void main(String[]args){int i=1,sum=0;for(;i<=9;i++)sum+ =i;System.out.println(sum);}1.7public class Test{public static void main(String[]args){System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11));System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11+1.0/13));}}1.8public class Test{public static void main(String[]args){final double PI=3.14; double radius=5.5;System.out.println(2*radius*PI);System.out.println(PI*radius*radius);}}1.9public class Test{public static void main(String[]args){System.out.println(7.9*4.5);System.out.p rintln(2*(7.9+4.5));}}1.10public class Test{public static void main(String[]args){double S=14/1.6;double T=45*60+30;double speed=S/T;System.out.println(speed);}1.11public class Test{public static void main(String[]args){int BN=312032486; //original person numbers double EveryYS,EveryYBP,EveryYDP,EveryYMP;EveryY S=365*24*60*60;EveryYBP=EveryYS/7;EveryYDP=EveryYS/13;Every YMP=EveryYS/45;int FirstYP,SecondYP,ThirdYP,FourthYP,FivthYP;FirstYP=(int)(BN+EveryYBP+EveryYMP-EveryYDP);SecondYP=(int)(FirstYP +EveryYBP+EveryYMP-EveryYDP);ThirdYP=(int)(SecondYP+EveryYBP+Ev eryYMP-EveryYDP);FourthYP=(int)(ThirdYP+EveryYBP+EveryYMP-EveryYD P);FivthYP=(int)(FourthYP+EveryYBP+EveryYMP-EveryYDP);System.out.pri ntln(FirstYP);System.out.println(SecondYP);System.out.println(ThirdYP);Syste m.out.println(FourthYP);System.out.println(FivthYP);}}1.12public class Test{public static void main(String[]args){double S=24*1.6; double T=(1*60+40)*60+35;double speed=S/T;System.out.println(sp eed);}}1.13import java.util.Scanner;public class Test{public static void main(String[]args){Scanner input=new Scan ner(System.in);System.out.println("input a,b,c,d,e,f value please:");double a=input.nextDouble();double b=input.nextDouble();double c=input.nextDouble();double d=input. nextDouble();double e=input.nextDouble();第二章package cn.Testcx;import java.util.Scanner;public class lesson2{public static void main(String[]args){@SuppressWarnings("resource")Scanner in put=new Scanner(System.in);System.out.print("请输入一个摄氏温度：");double Celsius=input.nextDouble();double Fahrenheit=(9.0/5)*Celsius+3 2;System.out.println("摄氏温度："+Celsius+"度"+"转换成华氏温度为："+Fahrenheit+"度");System.out.print("请输入圆柱的半径和高：");double radius=input.nextDouble();int higth=input.nextInt();double are as=radius*radius*Math.PI;double volume=areas*higth;System.out.println("圆柱体的面积为："+areas);System.out.println("圆柱体的体积为："+volume);System.out.print("输入英尺数：");double feet=input.nextDouble();double meters=feet*0.305;System.out.print ln(feet+"英尺转换成米："+meters);System.out.print("输入一个磅数：");double pounds=input.nextDouble();double kilograms=pounds*0.454;Syste m.out.println(pounds+"磅转换成千克为："+kilograms);System.out.println("输入分钟数：");long minutes=input.nextInt();long years=minutes/(24*60*365);long days=(minutes%(24*60*365))/(24*60);System.out.println(minutes+"分钟"+"有"+years+"年和"+days+"天");long totalCurrentTimeMillis=System.currentTimeMillis();long totalSeconds=t otalCurrentTimeMillis/1000;long currentSeconds=totalSeconds%60;long totalM inutes=totalSeconds/60;long currentMinutes=(totalSeconds%(60*60))/60;long currenthours=(totalMinutes/60)%24;System.out.print("输入时区偏移量：");byte zoneOffset=input.nextByte();long currentHour=(currenthours+(zoneOf fset*1))%24;System.out.println("当期时区的时间为："+currentHour+"时"+currentMinutes+"分"+currentSeconds+"秒");System.out.print("请输入v0,v1,t:");double v0=input.nextDouble();double v1=input.nextDouble();doublet=input.nextDouble();float a=(float)((v1-v0)/t);System.out.println("平均加速度a="+a);System.out.println("输入水的重量、初始温度、最终温度：");double water=input.nextDouble();double initialTemperature=input.nextDou ble();double finalTemperature=input.nextDouble();double Q=water*(finalTemp erature-initialTemperature)*4184;System.out.println("所需热量为："+Q);System.out.print("输入年数：");int numbers=input.nextInt();long oneYearsSecond=365*24*60*60;Longpop ulation=(long)((312032486+((oneYearsSecond/7.0)+(oneYearsSecond/45.0)-(oneYearsSecond/13.0))*numbers));System.out.println("第"+numbers+"年后人口总数为："+population);System.out.print("输入速度单位m/s和加速度a单位m/s2:");double v=input.nextDouble();double a1=input.nextDouble();double l engthOfAirplane=(Math.pow(v,2))/(2*a1);System.out.println("最短长度为："+lengthOfAirplane);System.out.print("输入存入的钱：");double money=input.nextInt();double monthRate=5.0/1200;for(int i=1;i<7; i++){double total=money*(Math.pow(1+monthRate,i));System.out.println("第"+i+"个月的钱为："+total);//告诉我书上的银行在哪里，我要去存钱，半年本金直接翻6倍、、、}System.out.print("用户请输入身高(英寸)、体重(磅):");double height=input.nextDouble();double weight=input.nextDouble(); double BMI=(weight*0.45359237)/(Math.pow((height*0.0254),2));System.out.println("BMI的值为"+BMI);System.out.print("输入x1和y1:");System.out.print("输入x2和y2:");double x1=input.nextDouble();double y1=input.nextDouble();double x2 =input.nextDouble();double y2=input.nextDouble();double point1=Math.pow((x2-x1),2);double point2=Math.pow((y2-y1),2);double distance=Math.pow((point1+point2),(1.0/2));//也可以Math.pow((point1+point2),0.5)System.out.println("两点间的距离为："+distance);System.out.print("输入六边形的边长：");double side=input.nextDouble();double area=(3*(Math.pow(3,0.5))*(Math.p ow(side,2)))/2;System.out.println("六边形的面积为："+area);}}。

《Java语言程序设计（基础篇）》（第10版梁勇著）第九章练习题答案9.1public class Exercise09_01 {public static void main(String[] args) {MyRectangle myRectangle = new MyRectangle(4, 40);System.out.println("The area of a rectangle with width " +myRectangle.width + " and height " +myRectangle.height + " is " +myRectangle.getArea());System.out.println("The perimeter of a rectangle is " +myRectangle.getPerimeter());MyRectangle yourRectangle = new MyRectangle(3.5, 35.9);System.out.println("The area of a rectangle with width " +yourRectangle.width + " and height " +yourRectangle.height + " is " +yourRectangle.getArea());System.out.println("The perimeter of a rectangle is " +yourRectangle.getPerimeter());}}class MyRectangle {// Data membersdouble width = 1, height = 1;// Constructorpublic MyRectangle() {}// Constructorpublic MyRectangle(double newWidth, double newHeight) {width = newWidth;height = newHeight;}public double getArea() {return width * height;}public double getPerimeter() {return 2 * (width + height);}}9.2public class Exercise09_02 {public static void main(String[] args) {Stock stock = new Stock("SUNW", "Sun MicroSystems Inc."); stock.setPreviousClosingPrice(100);// Set current pricestock.setCurrentPrice(90);// Display stock infoSystem.out.println("Previous Closing Price: " +stock.getPreviousClosingPrice());System.out.println("Current Price: " +stock.getCurrentPrice());System.out.println("Price Change: " +stock.getChangePercent() * 100 + "%");}}class Stock {String symbol;String name;double previousClosingPrice;double currentPrice;public Stock() {}public Stock(String newSymbol, String newName) {symbol = newSymbol;name = newName;}public double getChangePercent() {return (currentPrice - previousClosingPrice) /previousClosingPrice;}public double getPreviousClosingPrice() {return previousClosingPrice;}public double getCurrentPrice() {return currentPrice;}public void setCurrentPrice(double newCurrentPrice) {currentPrice = newCurrentPrice;}public void setPreviousClosingPrice(double newPreviousClosingPrice) { previousClosingPrice = newPreviousClosingPrice;}}9.3public class Exercise09_03 {public static void main(String[] args) {Date date = new Date();int count = 1;long time = 10000;while (count <= 8) {date.setTime(time);System.out.println(date.toString());count++;time *= 10;}}}9.4public class Exercise09_04 {public static void main(String[] args) {Random random = new Random(1000);for (int i = 0; i < 50; i++)System.out.print(random.nextInt(100) + " ");}9.5public class Exercise09_05 {public static void main(String[] args) {GregorianCalendar calendar = new GregorianCalendar();System.out.println("Year is " + calendar.get(GregorianCalendar.YEAR)); System.out.println("Month is " + calendar.get(GregorianCalendar.MONTH)); System.out.println("Date is " + calendar.get(GregorianCalendar.DATE));calendar.setTimeInMillis(1234567898765L);System.out.println("Year is " + calendar.get(GregorianCalendar.YEAR)); System.out.println("Month is " + calendar.get(GregorianCalendar.MONTH)); System.out.println("Date is " + calendar.get(GregorianCalendar.DATE)); }}9.6public class Exercise09_06 {static String output = "";/** Main method */public static void main(String[] args) {Scanner input = new Scanner(System.in);// Prompt the user to enter yearSystem.out.print("Enter full year (i.e. 2001): ");int year = input.nextInt();// Prompt the user to enter monthSystem.out.print("Enter month in number between 1 and 12: ");int month = input.nextInt();// Print calendar for the month of the yearprintMonth(year, month);System.out.println(output);}/** Print the calendar for a month in a year */static void printMonth(int year, int month) {// Get start day of the week for the first date in the monthint startDay = getStartDay(year, month);// Get number of days in the monthint numOfDaysInMonth = getNumOfDaysInMonth(year, month);// Print headingsprintMonthTitle(year, month);// Print bodyprintMonthBody(startDay, numOfDaysInMonth);}/** Get the start day of the first day in a month */static int getStartDay(int year, int month) {// Get total number of days since 1/1/1800int startDay1800 = 3;long totalNumOfDays = getTotalNumOfDays(year, month);// Return the start dayreturn (int)((totalNumOfDays + startDay1800) % 7);}/** Get the total number of days since Jan 1, 1800 */static long getTotalNumOfDays(int year, int month) {long total = 0;// Get the total days from 1800 to year -1for (int i = 1800; i < year; i++)if (isLeapYear(i))total = total + 366;elsetotal = total + 365;// Add days from Jan to the month prior to the calendar month for (int i = 1; i < month; i++)total = total + getNumOfDaysInMonth(year, i);return total;}/** Get the number of days in a month */static int getNumOfDaysInMonth(int year, int month) {if (month == 1 || month==3 || month == 5 || month == 7 ||month == 8 || month == 10 || month == 12)return 31;if (month == 4 || month == 6 || month == 9 || month == 11)return 30;if (month == 2)if (isLeapYear(year))return 29;elsereturn 28;return 0; // If month is incorrect.}/** Determine if it is a leap year */static boolean isLeapYear(int year) {if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) return true;return false;}/** Print month body */static void printMonthBody(int startDay, int numOfDaysInMonth) { // Pad space before the first day of the monthint i = 0;for (i = 0; i < startDay; i++)output += " ";for (i = 1; i <= numOfDaysInMonth; i++) {if (i < 10)output += " " + i;elseoutput += " " + i;if ((i + startDay) % 7 == 0)output += "\n";}output += "\n";}/** Print the month title, i.e. May, 1999 */static void printMonthTitle(int year, int month) {output += " " + getMonthName(month)+ ", " + year + "\n";output += "-----------------------------\n";output += " Sun Mon Tue Wed Thu Fri Sat\n";}/** Get the English name for the month */static String getMonthName(int month) {String monthName = null;switch (month) {case 1: monthName = "January"; break;case 2: monthName = "February"; break;case 3: monthName = "March"; break;case 4: monthName = "April"; break;case 5: monthName = "May"; break;case 6: monthName = "June"; break;case 7: monthName = "July"; break;case 8: monthName = "August"; break;case 9: monthName = "September"; break;case 10: monthName = "October"; break;case 11: monthName = "November"; break;case 12: monthName = "December";}return monthName;}}9.7public class Exercise09_07 {public static void main (String[] args) {Account account = new Account(1122, 20000);Account.setAnnualInterestRate(4.5);account.withdraw(2500);account.deposit(3000);System.out.println("Balance is " + account.getBalance()); System.out.println("Monthly interest is " +account.getMonthlyInterest());System.out.println("This account was created at " +account.getDateCreated());}}class Account {private int id;private double balance;private static double annualInterestRate;private java.util.Date dateCreated;public Account() {dateCreated = new java.util.Date();}public Account(int newId, double newBalance) {id = newId;balance = newBalance;dateCreated = new java.util.Date();}public int getId() {return this.id;}public double getBalance() {return balance;}public static double getAnnualInterestRate() {return annualInterestRate;}public void setId(int newId) {id = newId;}public void setBalance(double newBalance) {balance = newBalance;}public static void setAnnualInterestRate(double newAnnualInterestRate) { annualInterestRate = newAnnualInterestRate;}public double getMonthlyInterest() {return balance * (annualInterestRate / 1200);}public java.util.Date getDateCreated() { return dateCreated;}public void withdraw(double amount) {balance -= amount;}public void deposit(double amount) {balance += amount;}}9.8public class Exercise09_08 {public static void main(String[] args) { Fan1 fan1 = new Fan1();fan1.setSpeed(Fan1.FAST);fan1.setRadius(10);fan1.setColor("yellow");fan1.setOn(true);System.out.println(fan1.toString());Fan1 fan2 = new Fan1();fan2.setSpeed(Fan1.MEDIUM);fan2.setRadius(5);fan2.setColor("blue");fan2.setOn(false);System.out.println(fan2.toString()); }}class Fan1 {public static int SLOW = 1;public static int MEDIUM = 2;public static int FAST = 3;private int speed = SLOW;private boolean on = false;private double radius = 5;private String color = "white";public Fan1() {}public int getSpeed() {return speed;}public void setSpeed(int newSpeed) {speed = newSpeed;}public boolean isOn() {return on;}public void setOn(boolean trueOrFalse) {this.on = trueOrFalse;}public double getRadius() {return radius;}public void setRadius(double newRadius) { radius = newRadius;}public String getColor() {return color;}public void setColor(String newColor) {color = newColor;}@Overridepublic String toString() {return"speed " + speed + "\n"+ "color " + color + "\n"+ "radius " + radius + "\n"+ ((on) ? "fan is on" : " fan is off"); }}public class Exercise09_09 {public static void main(String[] args) {RegularPolygon polygon1 = new RegularPolygon();RegularPolygon polygon2 = new RegularPolygon(6, 4);RegularPolygon polygon3 = new RegularPolygon(10, 4, 5.6, 7.8);System.out.println("Polygon 1 perimeter: " +polygon1.getPerimeter());System.out.println("Polygon 1 area: " + polygon1.getArea());System.out.println("Polygon 2 perimeter: " +polygon2.getPerimeter());System.out.println("Polygon 2 area: " + polygon2.getArea());System.out.println("Polygon 3 perimeter: " +polygon3.getPerimeter());System.out.println("Polygon 3 area: " + polygon3.getArea());}}class RegularPolygon {private int n = 3;private double side = 1;private double x;private double y;public RegularPolygon() {}public RegularPolygon(int number, double newSide) {n = number;side = newSide;}public RegularPolygon(int number, double newSide, double newX, double newY) {n = number;side = newSide;x = newX;y = newY;}public int getN() {return n;}public void setN(int number) {n = number;}public double getSide() {return side;}public void setSide(double newSide) {side = newSide;}public double getX() {return x;}public void setX(double newX) {x = newX;}public double getY() {return y;}public void setY(double newY) {y = newY;}public double getPerimeter() {return n * side;}public double getArea() {return n * side * side / (Math.tan(Math.PI / n) * 4); }}9.10public class Exercise09_10 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a, b, c: ");double a = input.nextDouble();double b = input.nextDouble();double c = input.nextDouble();QuadraticEquation equation = new QuadraticEquation(a, b, c);double discriminant = equation.getDiscriminant();if (discriminant < 0) {System.out.println("The equation has no roots");}else if (discriminant == 0){System.out.println("The root is " + equation.getRoot1());}else// (discriminant >= 0){System.out.println("The roots are " + equation.getRoot1()+ " and " + equation.getRoot2());}}}class QuadraticEquation {private double a;private double b;private double c;public QuadraticEquation(double newA, double newB, double newC) {a = newA;b = newB;c = newC;}double getA() {return a;}double getB() {return b;}double getC() {return c;}double getDiscriminant() {return b * b - 4 * a * c;}double getRoot1() {if (getDiscriminant() < 0)return 0;else {return (-b + getDiscriminant()) / (2 * a);}}double getRoot2() {if (getDiscriminant() < 0)return 0;else {return (-b - getDiscriminant()) / (2 * a);}}}9.11public class Exercise09_11 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a, b, c, d, e, f: ");double a = input.nextDouble();double b = input.nextDouble();double c = input.nextDouble();double d = input.nextDouble();double e = input.nextDouble();double f = input.nextDouble();LinearEquation equation = new LinearEquation(a, b, c, d, e, f);if (equation.isSolvable()) {System.out.println("x is " +equation.getX() + " and y is " + equation.getY());}else {System.out.println("The equation has no solution");}}}class LinearEquation {private double a;private double b;private double c;private double d;private double e;private double f;public LinearEquation(double newA, double newB, double newC, double newD, double newE, double newF) {a = newA;b = newB;c = newC;d = newD;e = newE;f = newF;}double getA() {return a;}double getB() {return b;}double getC() {return c;}double getD() {return d;}double getE() {return e;}double getF() {return f;}boolean isSolvable() {return a * d - b * c != 0;}double getX() {double x = (e * d - b * f) / (a * d - b * c);return x;}double getY() {double y = (a * f - e * c) / (a * d - b * c);return y;}}9.12public class Exercise09_12 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter the endpoints of the first line segment: ");double x1 = input.nextDouble();double y1 = input.nextDouble();double x2 = input.nextDouble();double y2 = input.nextDouble();System.out.print("Enter the endpoints of the second line segment: ");double x3 = input.nextDouble();double y3 = input.nextDouble();double x4 = input.nextDouble();double y4 = input.nextDouble();// Build a 2 by 2 linear equationdouble a = (y1 - y2);double b = (-x1 + x2);double c = (y3 - y4);double d = (-x3 + x4);double e = -y1 * (x1 - x2) + (y1 - y2) * x1;double f = -y3 * (x3 - x4) + (y3 - y4) * x3;LinearEquation equation = new LinearEquation(a, b, c, d, e, f);if (equation.isSolvable()) {System.out.println("The intersecting point is: (" +equation.getX() + ", " + equation.getY() + ")");}else {System.out.println("The two lines do not cross ");}}}9.13public class Exercise09_13 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter the number of rows and columns of the array: ");int numberOfRows = input.nextInt();int numberOfColumns = input.nextInt();double[][] a = new double[numberOfRows][numberOfColumns];System.out.println("Enter the array: ");for (int i = 0; i < a.length; i++)for (int j = 0; j < a[i].length; j++)a[i][j] = input.nextDouble();Location location = locateLargest(a);System.out.println("The location of the largest element is " + location.maxValue + " at ("+ location.row + ", " + location.column + ")");}public static Location locateLargest(double[][] a) {Location location = new Location();location.maxValue = a[0][0];for (int i = 0; i < a.length; i++)for (int j = 0; j < a[i].length; j++) {if (location.maxValue < a[i][j]) {location.maxValue = a[i][j];location.row = i;location.column = j;}}return location;}}class Location {int row, column;double maxValue;}9.14public class Exercise09_14 {public static void main(String[] args) {int size = 100000;double[] list = new double[size];for (int i = 0; i < list.length; i++) {list[i] = Math.random() * list.length;}StopWatch stopWatch = new StopWatch();selectionSort(list);stopWatch.stop();System.out.println("The sort time is " + stopWatch.getElapsedTime()); }/** The method for sorting the numbers */public static void selectionSort(double[] list) {for (int i = 0; i < list.length - 1; i++) {// Find the minimum in the list[i..list.length-1]double currentMin = list[i];int currentMinIndex = i;for (int j = i + 1; j < list.length; j++) {if (currentMin > list[j]) {currentMin = list[j];currentMinIndex = j;}}// Swap list[i] with list[currentMinIndex] if necessary;if (currentMinIndex != i) {list[currentMinIndex] = list[i];list[i] = currentMin;}}}}class StopWatch {private long startTime = System.currentTimeMillis(); private long endTime = startTime;public StopWatch() {}public void start() {startTime = System.currentTimeMillis();}public void stop() {endTime = System.currentTimeMillis();}public long getElapsedTime() {return endTime - startTime;}}。

j a v a语言程序设计基础篇第十版练习答案精编Document number：WTT-LKK-GBB-08921-EIGG-2298601import class Exercise14_01 extendsApplication {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}02import class Exercise14_02 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}03import class Exercise14_03 extends Application {@Override One is to use the hint in the book.ArrayList<Integer> list = new ArrayList<>(); for (int i = 1; i <= 52; i++) {(i);}HBox pane = new HBox(5);;().add(new ImageView("image/card/" + (0) +".png"));().add(new ImageView("image/card/" + (1) +".png"));().add(new ImageView("image/card/" + (2) +".png"));Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}04import class Exercise14_04 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}06import class Exercise14_06 extends Application {@Override dd(rectangle);}}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}07import class Exercise14_07 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}08import class Exercise14_08 extends Application {@Override ng"), j, i);}}Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}09import class Exercise14_09 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class FanPane extends Pane {double radius = 50;public FanPane() {Circle circle = new Circle(60, 60, radius);;;getChildren().add(circle);Arc arc1 = new Arc(60, 60, 40, 40, 30, 35);; ddAll(arc1, arc2, arc3, arc4);}}10import class Exercise14_10 extends Application {@Override ddAll, ;Arc arc2 = new Arc(100, 140, 50, 20, 180, 180); ;;().addAll(ellipse, arc1, arc2,new Line(50, 40, 50, 140), new Line(150, 40, 150, 140));Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}11import class Exercise14_11 extends Application {@Override ddAll(circle, ellipse1, ellipse2,circle1, circle2, line1, line2, line3, arc);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}12import class Exercise14_12 extends Application {@Override ddAll(r1, text1, r2, text2, r3, text3, r4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}13import class Exercise14_13 extends Application {@Override ddAll(arc1, text1, arc2, text2, arc3, text3, arc4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}14import class Exercise14_14 extends Application {@Override ddAll(r1, r2, line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}15import class Exercise14_15 extends Application {@Override ddAll(polygon, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}16import class Exercise14_16 extends Application {@Override ind().divide(3));().bind());().bind().divide(3));;Line line2 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind());().bind().multiply(2).divide(3));;Line line3 = new Line(0, 0, 0, 0);().bind().divide(3));().bind().divide(3));().bind());;Line line4 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind().multiply(2).divide(3));().bind());;().addAll(line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}17import class Exercise14_17 extends Application {@Override ddAll(arc, line1, line2, line3, circle, line4, line5, line6, line7, line8);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}18import class Exercise14_18 extends Application {@Override ddAll(polyline, line1, line2,line3, line4, line5, line6, text1, text2);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}19import class Exercise14_19 extends Application {@Override ddAll(polyline1, polyline2, line1,line2,line3, line4, line5, line6, text1, text2,text3,text4, text5, text6, text7);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}20import class Exercise14_20 extends Application {@Override dd(new Line(x1, y1, x2, y2));dd(new Line(x2, y2, (x2 + (arctan + set45) * arrlen)),((y2)) + (arctan + set45) * arrlen)));().add(new Line(x2, y2, (x2 + (arctan - set45) * arrlen)),((y2)) + (arctan - set45) * arrlen)));}/*** The main method is only needed for the IDE with limited* JavaFX support. Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}21import class Exercise14_21 extends Application {@Override istance(x2, y2) + "");().addAll(circle1, circle2, line, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}22import class Exercise14_22 extends Application {@Override ddAll(circle1, circle2, line, text1, text2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}23import class Exercise14_23 extends Application {@Override ddAll(r1, r2, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}24import class Exercise14_24 extends Application {@Override ddAll(polygon, new Circle(x5, y5, 10), text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}25import class Exercise14_25 extends Application {@Override ddAll(circle, polygon);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}26import class Exercise14_26 extends Application {@Override ddAll(clock1, clock2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}27import class Exercise14_27 extends Application {@OverrideNot needed for running from the command line. */public static void main(String[] args) {launch(args);}}class DetailedClockPane extends Pane {private int hour;private int minute;private int second;lear();getChildren().addAll(circle, sLine, mLine, hLine);dd(new Line(xOuter, yOuter, xInner, yInner));}dd(text);}}}28import class Exercise14_28 extends Application {@OverrideNot needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class ClockPaneWithBooleanProperties extends Pane { private int hour;private int minute;private int second;private boolean hourHandVisible = true;private boolean minuteHandVisible = true; private boolean secondHandVisible = true;public boolean isHourHandVisible() {return hourHandVisible;}public void setHourHandVisible(boolean hourHandVisible) {= hourHandVisible;paintClock();}public boolean isMinuteHandVisible() {return minuteHandVisible;}public void setMinuteHandVisible(boolean minuteHandVisible) {= minuteHandVisible;paintClock();}public boolean isSecondHandVisible() {return secondHandVisible;public void setSecondHandVisible(boolean secondHandVisible) {= secondHandVisible;paintClock();}lear();getChildren().addAll(circle, t1, t2, t3, t4);if (secondHandVisible) {getChildren().add(sLine);}if (minuteHandVisible) {getChildren().add(mLine);}if (hourHandVisible) {getChildren().add(hLine);}}}import class Exercise14_29 extends Application {final static double HGAP = 20;final static double VGAP = 20;final static double RADIUS = 5;final static double LENGTH_OF_SLOTS = 40;final static double LENGTH_OF_OPENNING = 15;final static double Y_FOR_FIRST_NAIL = 50;final static double NUMBER_OF_SLOTS = 9;final static double NUMBER_OF_ROWS =NUMBER_OF_SLOTS - 2;@Override dd(c);}}dd(new Line(x, y, x, y + LENGTH_OF_SLOTS)); }dd(new Line(centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP,y + LENGTH_OF_SLOTS, centerX -(NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP,y + LENGTH_OF_SLOTS));dd(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP, y));().add(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP, y));dd(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));().add(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX + HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));Not needed for running from the command line.*/public static void main(String[] args) { launch(args);}}。

java语言程序设计课后习题答案Java语言程序设计是计算机科学与技术专业的重要课程之一，通过课后习题的解答，可以帮助学生巩固所学知识，提高编程能力。

本文将回答一些Java语言程序设计的常见习题，帮助读者更好地理解与运用Java语言。

1. 基本数据类型Java中的基本数据类型有byte、short、int、long、float、double、char和boolean。

它们分别用于表示不同的数据类型，如整数、浮点数、字符和布尔值等。

在Java中，基本数据类型的大小是固定的，不会受到不同机器架构的影响。

2. 变量与常量在Java中，使用关键字"var"、"final"和数据类型来声明变量。

变量可以根据需要进行赋值与修改。

而常量在声明时需要使用关键字"final"来修饰，并且一旦赋值后就不能再修改。

3. 运算符Java中的运算符有算术运算符、赋值运算符、关系运算符、逻辑运算符和位运算符等。

它们用于执行不同的操作，如数学运算、赋值、比较和逻辑判断等。

4. 条件语句条件语句用于根据条件来执行不同的代码块。

Java中的条件语句有if语句、if-else语句、switch语句等。

通过条件语句，可以根据不同的条件来执行相应的代码逻辑。

5. 循环语句循环语句用于重复执行一段代码块。

Java中的循环语句有for循环、while循环和do-while循环等。

通过循环语句，可以方便地处理需要重复执行的操作。

6. 数组数组是一种存储相同类型数据的集合。

在Java中，数组可以存储基本数据类型或引用类型的数据。

数组有固定的长度，在声明时需要指定数组的大小，并且可以通过索引访问数组中的元素。

7. 方法方法用于封装一段特定的代码，可以通过方法名来调用执行。

Java中的方法可以有返回值，也可以没有返回值。

通过方法的调用，可以提高代码的复用性和可读性。

8. 类与对象类是面向对象编程的基本单位，用于封装数据和方法。

Java语言程序设计课后习题答案全集Java语言程序设计是一门广泛应用于软件开发领域的编程语言，随着其应用范围的不断扩大，对于掌握Java编程技巧的需求也逐渐增加。

为了帮助读者更好地掌握Java编程，本文将提供Java语言程序设计课后习题的全集答案，供读者参考。

一、基础知识题1. 代码中的注释是什么作用？如何使用注释.答：注释在代码中是用来解释或者说明代码的功能或用途的语句，编译器在编译代码时会自动忽略注释。

在Java中，有三种注释的方式：- 单行注释：使用"// " 可以在代码的一行中加入注释。

- 多行注释：使用"/* */" 可以在多行中添加注释。

- 文档注释：使用"/** */" 可以添加方法或类的文档注释。

2. 什么是Java的数据类型？请列举常见的数据类型。

答：Java的数据类型用来指定变量的类型，常见的数据类型有：- 基本数据类型：包括整型（byte、short、int、long）、浮点型（float、double）、字符型（char）、布尔型（boolean）。

- 引用数据类型：包括类（class）、接口（interface）、数组（array）等。

二、代码编写题1. 编写Java程序，输入两个整数，求和并输出结果。

答：```javaimport java.util.Scanner;public class SumCalculator {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.print("请输入第一个整数：");int num1 = scanner.nextInt();System.out.print("请输入第二个整数：");int num2 = scanner.nextInt();int sum = num1 + num2;System.out.println("两个整数的和为：" + sum);}}```三、综合应用题1. 编写Java程序，实现学生信息管理系统，要求包括以下功能：- 添加学生信息（姓名、年龄、性别、学号等）；- 修改学生信息；- 删除学生信息；- 查询学生信息。

第一章1.1 public class Test{public static void main(String[] args){System.out.println("Welcome to Java !");System.out.println("Welcome to Computer Science !");System.out.println("Programming is fun .");}}1.2 public class Test{public static void main(String[] args){for(int i = 0;i <= 4;i++){System.out.println("Welcome to Java !");}}}1.3 public class Test{public static void main(String[] args){System.out.println(" ]");System.out.println(" ]");System.out.println("] ]");System.out.println(" ]]");}}public class Test{public static void main(String[] args){System.out.println(" A");System.out.println(" A A");System.out.println(" AAAAA");System.out.println("A A");}}public class Test{public static void main(String[] args){System.out.println("V V");System.out.println(" V V");System.out.println(" V V");System.out.println(" V");}}1.4 public class Test{public static void main(String[] args){System.out.println("a a^2 a^3");System.out.println("1 1 1");System.out.println("2 4 8");System.out.println("3 9 27");System.out.println("4 16 64");}}1.5 public class Test{public static void main(String[] args){System.out.println((9.5*4.5-2.5*3)/(45.5-3.5));}}1.6 public class Test{public static void main(String[] args){int i = 1,sum = 0;for(;i <= 9;i++)sum += i;System.out.println(sum);}}1.7 public class Test{public static void main(String[] args){System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11));System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11+1.0/13)) ;}}1.8 public class Test{public static void main(String[] args){final double PI = 3.14;double radius = 5.5;System.out.println(2 * radius * PI);System.out.println(PI * radius * radius);}}1.9 public class Test{public static void main(String[] args){System.out.println(7.9 * 4.5);System.out.println(2 * (7.9 + 4.5));}}1.10 public class Test{public static void main(String[] args){double S = 14 / 1.6;double T = 45 * 60 + 30;double speed = S / T;System.out.println(speed);}}1.11public class Test{public static void main(String[] args){int BN = 312032486; //original person numbersdouble EveryYS,EveryYBP,EveryYDP,EveryYMP;EveryYS = 365 * 24 * 60 * 60;EveryYBP = EveryYS / 7;EveryYDP = EveryYS / 13;EveryYMP = EveryYS / 45;int FirstYP,SecondYP,ThirdYP,FourthYP,FivthYP;FirstYP = (int)(BN + EveryYBP + EveryYMP - EveryYDP);SecondYP = (int)(FirstYP + EveryYBP + EveryYMP - EveryYDP);ThirdYP = (int)(SecondYP + EveryYBP + EveryYMP - EveryYDP);FourthYP = (int)(ThirdYP + EveryYBP + EveryYMP - EveryYDP);FivthYP = (int)(FourthYP + EveryYBP + EveryYMP - EveryYDP);System.out.println(FirstYP);System.out.println(SecondYP);System.out.println(ThirdYP);System.out.println(FourthYP);System.out.println(FivthYP);}}1.12 public class Test{public static void main(String[] args){double S = 24 * 1.6;double T = (1 * 60 + 40) * 60 + 35;double speed = S / T;System.out.println(speed);}}1.13 import java.util.Scanner;public class Test{public static void main(String[] args){Scanner input = new Scanner(System.in);System.out.println("input a,b,c,d,e,f value please:");double a = input.nextDouble();double b = input.nextDouble();double c = input.nextDouble();double d = input.nextDouble();double e = input.nextDouble();double f = input.nextDouble();double x,y;x = (e * d - b * f) / (a * d - b * c);y = (a * f - e * c) / (a * d - b * c);System.out.println("The result is x: "+(int)(x * 1000) / 1000.0);System.out.println("The result is y: "+(int)(y * 1000) / 1000.0);}}。

3.4import javax.swing.*;public class AdditionTutor{public static void main(String[] args){int number1=(int)(System.currentTimeMillis()%100);int number2=(int)(System.currentTimeMillis()*5%100);String answerString=JOptionPane.showInputDialog("what is "+ number1 +"+ "+ number2+" ?");int answer=Integer.parseInt(answerString);JOptionPane.showMessageDialog(null,number1 +" + "+ number2 +" = "+answer+" is "+(number1+number2==answer));}}3.10import javax.swing.JOptionPane;public class ComputeTaxWithSelectionStatement{public static void main(String[] args){//Prompt the user to enter filing statusString statusString = JOptionPane.showInputDialog("Enter the filing status:\n"+"(0-single filer,1-married jointly,\n"+"2-married separately,3-head of household)");int status = Integer.parseInt(statusString);//Prompt the user to enter taxable incomeString incomeString = JOptionPane.showInputDialog("Enter the taxable income:");double income = Double.parseDouble(incomeString);//Comput taxdouble tax=0;if (status == 0){//Compute tax for single filersif (income <= 6000)tax = income * 0.10;else if (income <= 27950)tax = 6000 * 0.10 + (income - 6000) * 0.15;else if (income <= 67700)tax = 6000 * 0.10 + (27950 - 6000) * 0.15 +(income - 27950) * 0.27;else if (income <= 141250)tax = 6000 * 0.10 + (27950 - 6000) * 0.15 +(67700 - 27950) * 0.27 + (income - 67700) * 0.30;else if (income <=307050)tax = 6000 * 0.10 + (27950 - 6000) * 0.15 +(67700 - 27950) * 0.27 + (141250 - 67700) * 0.30 +(income - 141250) * 0.35;elsetax = 6000 * 0.10 + (27950 - 6000) * 0.15 +(67700 - 27950) * 0.27 + (141250 -67700) * 0.30 +(307050 - 141250) * 0.35 + (income - 307050) * 0.386;}else if (status == 1){//Compute tax for married file jointly if (income <= 12000)tax = income * 0.10;else if (income <= 46700)tax = 12000 * 0.10 + (income - 12000) * 0.15;else if (income <= 112850)tax = 12000 * 0.10 + (46700 - 12000) * 0.15 +(income - 46700) * 0.27;else if (income <= 171950)tax = 12000 * 0.10 + (46700 - 12000) * 0.15 +(112850 - 46700) * 0.27 + (income - 112850) * 0.30;else if (income <= 307050)tax = 12000 * 0.10 + (46700 - 12000) * 0.15 +(112850 - 46700) * 0.27 + (141250 - 112850) * 0.30 +(income - 307050) * 0.35;elsetax = 12000 * 0.10 + (46700 - 12000) * 0.15 +(112850 - 46700 ) * 0.27 + (171950 - 112850) * 0.30 +(307050 - 171950) * 0.35 + (income - 307050) * 0.386;}else if (status == 2){//Compute tax for married separately if (income <= 6000)tax = income * 0.10;else if (income <= 23350)tax = 6000 * 0.10 + (income - 6000) * 0.15;else if (income <= 56425)tax = 6000 * 0.10 + (23350 - 6000) * 0.15 +(income - 23350) * 0.27;else if (income <= 85975)tax = 6000 * 0.10 + (23350 - 6000) * 0.15 +(56425 - 23350) * 0.27 + (income - 56425) * 0.30;else if (income <= 153525)tax = 6000 * 0.10 + (23350 - 6000) * 0.15 +(56425 - 23350) * 0.27 + (85975 - 56425) * 0.30 +(income - 85975) * 0.35;elsetax = 6000 * 0.10 + (23350 - 6000) * 0.15 +(56425 - 23350) * 0.27 + (85975 - 56425) * 0.30 +(153525 - 85975) * 0.35 + (income - 153525) * 0.386;}else if (status == 3){//Compute tax for head of householdif (income <= 10000)tax = income * 0.10;else if (income <= 37450)tax = 10000 * 0.10 + (income - 10000) * 0.15;else if (income <= 96700)tax = 10000 * 0.10 + (37450 - 10000) * 0.15 +(income - 37450) * 0.27;else if (income <= 156600)tax = 10000 * 0.10 + (37450 - 10000) * 0.15 +(96700 - 37450) * 0.27 + (income - 96700) * 0.30;else if (income <= 307050)tax = 10000 * 0.10 + (37450 - 10000) * 0.15 +(96700 - 37450) * 0.27 + (156600 - 96700) * 0.30 +(income - 156600) * 0.35;elsetax = 10000 * 0.10 + (37450 - 10000) * 0.15 +(96700 - 37450) * 0.27 + (156600 - 96700) * 0.30 +(307050 - 156600) * 0.35 + (income - 307050) * 0.386;}else{System.out.println("Error: invalid status");System.exit(0);}//Display the resultJOptionPane.showMessageDialog(null,"Tax is " +(int)(tax * 100) / 100.0);}}4.11public class ZhengChu{public static void main(String[] args){int count=0;for(int i=100;i<=200;i++){if((i%5==0||i%6==0)&&i%30!=0){System.out.print(" "+ i);count++;if(count%10==0)System.out.println();}}}}4.14public class ASCII{public static void main(String[] args){int count = 0;for(int i = 33; i <= 126; i++){count++;char ch = (char)i;System.out.print(" " + ch);if(count % 10 == 0)System.out.println();}}}4.17import javax.swing.JOptionPane;public class FindSalesAmount{/**Main method*/public static void main(String[] args){//The commission soughtString COMMISSION_SOUGHTString = JOptionPane.showInputDialog("Enter the COMMISSION_SOUGHT :");double COMMISSION_SOUGHT = Double.parseDouble(COMMISSION_SOUGHTString);double commission = 0;double salesAmount;for (salesAmount = 0.01;commission <= COMMISSION_SOUGHT;){salesAmount += 0.01; //防止犯off-by-one错误，先判断在做自加！if (salesAmount >= 10000.01)commission =5000 * 0.08 + 5000 * 0.1 + (salesAmount - 10000) * 0.12;else if (salesAmount >= 5000.01)commission = 5000 * 0.08 + (salesAmount - 5000) * 0.10;elsecommission = salesAmount * 0.08;}String output ="The sales amount $" + (int)(salesAmount * 100) / 100.0 +"\n is needed to make a commission of $" + COMMISSION_SOUGHT;JOptionPane.showMessageDialog(null,output);}}5.6import javax.swing.JOptionPane;public class PrintPyramid{public static void main(String[] args){String input = JOptionPane.showInputDialog("Enter the number of lines:");int numberOfLines = Integer.parseInt(input);displayPattern(numberOfLines);}public static void displayPattern(int n){for (int row = 1;row <= n;row++){for (int column = 1;column <= n - row;column++)System.out.print(" ");for (int num = row;num >= 1;num--)System.out.print((num >= 10) ? " " + num : " " + num);System.out.println();}}}5.18public class MathSuanFa{public static void main(String[] args){double A = Math.sqrt(4);double B = (int)Math.sin(2 * Math.PI);double C = (int)Math.cos(2 * Math.PI);double D = (int)Math.pow(2, 2);double E = (int)Math.log(Math.E);double F = (int)(Math.exp(1)*100000)/100000.0;double G = (int)Math.max(2, Math.min(3, 4));double H = (int)Math.rint(-2.5);double I = (int)Math.ceil(-2.5);double J = (int)Math.floor(-2.5);int K = (int)Math.round(-2.5f);int L = (int)Math.round(-2.5);double M = (int)Math.rint(2.5);double N = (int)Math.ceil(2.5);double O = (int)Math.floor(2.5);int P = (int)Math.round(2.5f);int Q = (int)Math.round(2.5);int R = (int)Math.round(Math.abs(-2.5));System.out.println(A +" "+ B +" "+ C +" "+ D +" "+ E +" "+ F +" "+ G +" "+ H +" "+ I +" "+ J +" "+ K +" "+ L +" "+ M +" "+ N +" "+ O +" "+ P +" "+ Q +" "+ R);}}6.9import javax.swing.JOptionPane;public class Array{public static void main (String[] args){String incomeString = JOptionPane.showInputDialog("Enter the number of array size:");int income = Integer.parseInt(incomeString);int arraySize = income;int [] myList = new int [arraySize];int m;for ( m = 0; m < arraySize; m++){String elementString = JOptionPane.showInputDialog("Enter the " + (m + 1) + " element of the array");int element = Integer.parseInt(elementString);myList[m] = element;}int minElement = myList[0];for (int i=1; i < arraySize; i++){if (myList[i] < minElement)minElement = myList[i];}JOptionPane.showMessageDialog(null,"The min element is: " + minElement); }}。

java基础篇第十版复习题答案1. 简述Java中基本数据类型及其大小。

答案：Java中的基本数据类型包括：byte（8位），short（16位），int（32位），long（64位），float（32位），double（64位），char（16位）和boolean（1位）。

2. 描述Java中类和对象的关系。

答案：类是对象的蓝图或模板，定义了对象的属性和方法。

对象是根据类创建的实例，具有类定义的属性和方法。

3. 说明Java中继承的概念及其特点。

答案：继承是Java中的一种机制，允许一个类（子类）继承另一个类（父类）的属性和方法。

特点包括代码重用、扩展性和实现多态。

4. 阐述Java中的接口是什么以及它的作用。

答案：接口在Java中是一种引用类型，它定义了一组方法规范，但不实现这些方法。

接口的作用是为不同的类提供统一的方法规范，实现多态。

5. 描述Java中异常处理的机制。

答案：Java中的异常处理机制包括try、catch和finally块。

try块用于捕获异常，catch块用于处理异常，finally块用于执行清理操作，无论是否发生异常。

6. 简述Java中集合框架的组成及其特点。

答案：Java集合框架主要由两大接口组成：Collection和Map。

Collection接口包括List、Set和Queue等子接口，用于存储单一元素。

Map接口用于存储键值对。

特点包括提供了统一的操作接口、支持泛型、实现了迭代器等。

7. 解释Java中多线程的概念及其实现方式。

答案：多线程是指程序中同时运行多个线程。

Java中实现多线程的方式包括继承Thread类和实现Runnable接口。

通过start()方法启动线程，线程执行run()方法。

8. 说明Java中垃圾回收机制的作用及其工作原理。

答案：垃圾回收机制的作用是自动回收不再使用的对象所占用的内存。

工作原理是通过引用计数或者标记-清除算法来识别无用对象，并释放其内存。

《Java语言程序设计（基础篇）》（第10版梁勇著）第二十一章练习题答案21.1import java.util.*;public class Exercise21_01 {public static void main(String[] args) {LinkedHashSet<String> set1 = new LinkedHashSet<String>(Arrays.asList( new String[]{"George", "Jim", "John", "Blake", "Kevin", "Michael"}));LinkedHashSet<String> set1Clone1 = (LinkedHashSet<String>)set1.clone(); LinkedHashSet<String> set1Clone2 = (LinkedHashSet<String>)set1.clone();LinkedHashSet<String> set2 = new LinkedHashSet<String>(Arrays.asList( new String[] {"George", "Katie", "Kevin", "Michelle", "Ryan"}));set1.addAll(set2);set1Clone1.removeAll(set2);set1Clone2.retainAll(set2);System.out.println("The union of the two sets is " + set1);System.out.println("The difference of the two sets is " + set1Clone1); System.out.println("The intersection of the two sets is " + set1Clone2); }}21.1附加import java.util.*;public class Exercise21_01Extra {public static void main(String[] args) {System.out.print("Enter a string: ");Scanner input = new Scanner(System.in);String s = input.nextLine();Character[] list1 = {'A', 'E', 'I', 'O', 'U'};Set<Character> vowels = new HashSet<>(Arrays.asList(list1));Set<Character> vowelsInString = new HashSet<>();Set<Character> consonantsInString = new HashSet<>();int numbeOfVowels = 0;int numbeOfConsonants = 0;for (int i = 0; i < s.length(); i++) {char ch = Character.toUpperCase(s.charAt(i));if (Character.isLetter(ch)) {if (vowels.contains(ch)) {if (!vowelsInString.contains(ch)) {vowelsInString.add(ch);numbeOfVowels++;}}else if (!consonantsInString.contains(ch)) {consonantsInString.add(ch);numbeOfConsonants++;}}}System.out.println("The number of vowels is " + numbeOfVowels);System.out.println("The number of consonants is " + numbeOfConsonants); }}21.2import java.util.*;import java.io.*;public class Exercise21_02 {public static void main(String[] args) {if (args.length != 1) {System.out.println("Usage: java Exercise21_02 fullfilename");System.exit(1);}String filename = args[0];// Create a tree set to hold the wordsTreeSet<String> treeSet = new TreeSet<String>();try {Scanner in = new Scanner(new File(filename));String line;while ((line = in.nextLine()) != null) {String[] tokens = line.split("[ |\n|\t|\r|.|,|)|(|-|\"]");for (int i = 0; i < tokens.length; i++)treeSet.add(tokens[i]);}}catch (Exception ex) {System.err.println(ex);}// Get an iterator for the setIterator iterator = treeSet.iterator();// Display mappingsSystem.out.println("\nDisplay words in ascending order ");while (iterator.hasNext()) {System.out.println(iterator.next());}}}21.3import java.util.*;import java.io.*;public class Exercise21_03 {public static void main(String[] args) {// Check usageif (args.length != 1) {System.out.println("Usage: java Exercise21_03 file.java");System.exit(1);}// Array of all Java keywords + true + nullString[] keywordString = {"abstract", "finally", "public", "boolean", "float", "return", "break", "for", "short", "byte","goto", "static", "case", "if", "super", "catch", "implements", "switch", "char", "import", "synchronized", "class","instanceof", "this", "const", "int", "throw", "continue","interface", "throws", "default", "long", "transient", "do","native", "try", "double", "new", "void", "else", "package","volatile", "extends", "private", "while", "final","protected", "true", "null"};Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));int count = 0;try {Scanner input = new Scanner(new File(args[0]));String text = "";while (input.hasNext()) {String line = input.nextLine();line = stripLineComments(line);line = stripLineStringLiterals(line);text += line + " ";}text = stripParagraghComments(text);String[] tokens = text.split("[ \\[,()\\]]");for (String token: tokens) {if (keywordSet.contains(token))count++;}System.out.println("The number of keywords in the program is " + count);}catch (Exception ex) {ex.printStackTrace();}}/* Strip line comments */private static String stripLineComments(String line) {int index = line.indexOf("//");if (index < 0)return line;elsereturn line.substring(0, index);}/* Strip string literals */private static String stripLineStringLiterals(String line) {int start = line.indexOf("\"");int end = line.indexOf("\"", start + 1);while (start > 0 && end > 0) {line = line.substring(0, start) + line.substring(end + 1);start = line.indexOf("\"");end = line.indexOf("\"");}return line;}/* Strip paragraph comments */private static String stripParagraghComments(String text) {int start = text.indexOf("/*");int end = text.indexOf("*/");while (start > 0 && end > 0) {text = text.substring(0, start) + text.substring(end + 2);start = text.indexOf("/*");end = text.indexOf("*/");}return text;}}/** This is an incorrect version. It does not count the case such as (this. Here the this keyword* is not counted. It does not exclude keywords in the comments*import java.util.*;import java.io.*;public class Exercise20_03 {public static void main(String[] args) {// Check usageif (args.length != 1) {System.out.println("Usage: java Exercise20_03 file.java");System.exit(0);}// Array of all Java keywords + true + nullString[] keywordString = {"abstract", "finally", "public","boolean", "float", "return", "break", "for", "short", "byte", "goto", "static", "case", "if", "super", "catch", "implements", "switch", "char", "import", "synchronized", "class","instanceof", "this", "const", "int", "throw", "continue","interface", "throws", "default", "long", "transient", "do","native", "try", "double", "new", "void", "else", "package","volatile", "extends", "private", "while", "final","protected", "true", "null"};Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));int count = 0;try {Scanner input = new Scanner(new File(args[0]));while (input.hasNext()) {String token = input.next();if (keywordSet.contains(token))count++;}System.out.println("The number of keywords in the program is " + count);}catch (Exception ex) {ex.printStackTrace();}}}*/21.4import java.util.Scanner;import java.util.HashSet;import java.util.Arrays;public class Exercise21_04 {public static void main(String[] args) throws Exception {HashSet<Character> set1 = new HashSet<Character>(Arrays.asList( new Character[]{'A', 'E', 'I', 'O', 'U'}));System.out.print("Enter a filename: ");Scanner input = new Scanner(System.in);String filename = input.nextLine();input = new Scanner(new java.io.File(filename));int countVowels = 0;int countConsonants = 0;while (input.hasNext()) {String s = input.nextLine().toUpperCase();for (int i = 0; i < s.length(); i++) {if (set1.contains(s.charAt(i)))countVowels++;else if (Character.isLetter(s.charAt(i)))countConsonants++;}}System.out.println("The number of vowels is " + countVowels + " and consonanats is " +countConsonants);}}21.5/*** Usage: Copy this class to the folder, run it with java JavaToHTMLftim * to generate* HTM file for all the .java file in this folder. The generated .htm files are* stored in the same folder*/import java.util.*;import java.io.*;public class Exercise21_05 {// Array of all Java keywords + true + false + nullstatic String[] keywordString = {"abstract", "assert", "boolean","break", "byte", "case", "catch", "char", "class", "const","continue", "default", "do", "double", "else", "enum","extends", "for", "final", "finally", "float", "goto", "if","implements", "import", "instanceof", "int", "interface","long", "native", "new", "package", "private", "protected","public", "return", "short", "static", "strictfp", "super","switch", "synchronized", "this", "throw", "throws","transient", "try", "void", "volatile", "while","true", "false", "null"};static Set<String> keywordSet =new HashSet<String>(Arrays.asList(keywordString));/** Main method */public static void main(String[] args) throws Exception {// Check usageif (args.length != 2) {System.out.println("Usage: java Exercise20_10 javaSourcefile htmlfile");System.exit(1);}Scanner input = new Scanner(new File(args[0]));PrintWriter output = new PrintWriter(new File(args[1]));JavaToHTML(input, output);}static boolean stringToken = false;static String inputFileName;public static void JavaToHTML(Scanner input, PrintWriter output) { try {output.format("%s\r\n", "<html>");output.format("%s\r\n", "<head>");output.format("%s\r\n","<title>Intro to Java Programming, 6E - " + inputFileName +"</title>");output.format("%s\r\n","<meta http-equiv=\"Content-Type\" content=\"text/html; charset=windows-1252\">");output.format("%s\r\n", "<style type = \"text/css\">");output.format("%s\r\n","body {font-family: \"Courier New\", sans-serif; font-size: 100%; color: black}");output.format("%s\r\n",".keyword {color: #000080; font-weight: bold}");output.format("%s\r\n", ".comment {color: #008000}");output.format("%s\r\n", ".literal {color: #0000ff}");// Match the color in the text// output.format("%s\r\n", ".keyword {color: black; font-weight: bold}");// output.format("%s\r\n", ".comment {color: #77797C}");// output.format("%s\r\n", ".literal {color: #007346; font-weight: bold}");output.format("%s\r\n", "</style>");output.format("%s\r\n", "</head>");output.format("%s\r\n", "<body>");output.format("%s\r\n", "<pre>");String text = "";String temp;// Read all lineswhile (input.hasNext()) {temp = input.nextLine();text += temp + "\r\n";}text = text.replaceAll(">", "&gt;");text = text.replaceAll("<", "&lt;");translateToHTML(text, input, output);output.format("%s\r\n", "</pre>");output.format("%s\r\n", "</body>");output.format("%s\r\n", "</html>");}catch (Exception ex) {System.out.println(ex);}finally {try {input.close();output.close();}catch (Exception ex) {}}}/** Translate Java source code to HTML */static void translateToHTML(String text, Scanner input, PrintWriter output) throws Exception {text = text.replaceAll("// ", "LINECOMMENT");text = text.replaceAll("/\\*", "BLOCKCOMMENT");String token;while (text != null && text.length() > 0) {// * and / are in conflict with /* and //String[] parts = text.split("[%\\+\\-\\*/\r\n\t \\[\\].;(){},]", 2); token = parts[0];if (token.length() > 1 && token.startsWith("LINECOMMENT")) {output.format("%s", "<span class = \"comment\">");parts = text.split("\r\n", 2);text = parts[1];output.format("%s", parts[0].replaceAll("LINECOMMENT", "// "));output.format("%s", "</span>\r\n");continue;}else if (token.length() > 1 && token.startsWith("BLOCKCOMMENT")) {output.format("%s", "<span class = \"comment\">");parts = text.split("\\*/", 2);text = parts[1];output.format("%s", parts[0].replaceAll("BLOCKCOMMENT", "/*") +"*/");output.format("%s", "</span>");continue;}else if (token.length() > 1 && token.matches("'\\w'*")) {output.format("%s", "<span class = \"literal\">");output.format("%s", token);output.format("%s", "</span>");}else if (token.startsWith("\"") && token.endsWith("\"") &&(token.length() > 1)) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.startsWith("'") && token.endsWith("'") &&(token.length() > 1)) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.equals("' '")) {output.format("%s", "<span class = \"literal\">" + token+ "</span>");}else if (token.startsWith("\"") && token.endsWith("\"") &&(token.length() == 1)) {if (stringToken) {output.format("%s", token + "</span>");stringToken = false;}else {output.format("%s", "<span class = \"literal\">" + token); stringToken = true;}}else if (token.startsWith("\"")) {output.format("%s", "<span class = \"literal\">" + token); stringToken = true;}else if (token.endsWith("\"") && (!token.endsWith("\\\""))) { output.format("%s", token);output.format("%s", "</span>");stringToken = false;}else if (token.matches("\\d+")) { // Check if numericoutput.format("%s", "<span class = \"literal\">" + token +"</span>");}else if (!stringToken && keywordSet.contains(token)) {output.format("%s", "<span class = \"keyword\">" + token +"</span>");}else {output.format("%s", token);}if (token.length() < text.length()) {if (text.charAt(token.length()) == '<')output.format("%s", "&lt;");else if (text.charAt(token.length()) == '>')output.format("%s", "&gt;");elseoutput.format("%s", text.charAt(token.length()));}if (parts.length == 2) {text = parts[1];}}}}21.6import java.util.*;public class Exercise21_06 {public static void main(String[] args) {// Create a tree map to hold words and key and count as value TreeMap<Integer, Integer> treeMap = new TreeMap<>();Scanner input = new Scanner(System.in);while (true) {// Enter an integerSystem.out.print("Enter an integer: ");int number = input.nextInt();if (number == 0) break;Integer key = new Integer(number);if (treeMap.get(key) != null) {int value = ((Integer)treeMap.get(key)).intValue();value++;treeMap.put(key, new Integer(value));}else {treeMap.put(key, new Integer(1));}}Integer max = Collections.max(treeMap.values());Set<Integer> keys = treeMap.keySet();Iterator<Integer> iterator = keys.iterator();while (iterator.hasNext()) {Object key = iterator.next();Integer value = (Integer)(treeMap.get(key));if (value.equals(max)) {System.out.println("Number " + key + " occurred most");}}}}21.7import java.util.*;public class Exercise21_07 {public static void main(String[] args) {// Text in a stringString text = "Have a good day. Have a good class. " + "Have a good visit. Have fun!";// Create a hash map to hold words and key and count as value HashMap<String, Integer> hashMap = new HashMap<>();String[] tokens = text.split("[ |.|!|?]");for (String key: tokens) {if (hashMap.get(key) != null) {hashMap.put(key, hashMap.get(key).intValue() + 1);}else {if (key.trim().length() > 0)hashMap.put(key, 1);}}// Get an entry set for the tree mapSet<Map.Entry<String, Integer>> entrySet = hashMap.entrySet();ArrayList<WordOccurrence> list = new ArrayList<>();for (Map.Entry<String, Integer> entry: entrySet) {list.add(new WordOccurrence(entry.getKey(), entry.getValue())); }Collections.sort(list);for (WordOccurrence item: list) {System.out.println(item);}}}class WordOccurrence implements Comparable<WordOccurrence> {String word;int count;public WordOccurrence(String word, int count) {this.word = word;this.count = count;}@Overridepublic int compareTo(WordOccurrence o) {return count - o.count;}@Overridepublic boolean equals(Object o) {return word.equals(((WordOccurrence)o).word);}@Overridepublic String toString() {return word + ": " + count;}}21.8import java.util.*;import java.io.*;public class Exercise21_08 {public static void main(String[] args) {if (args.length != 1) {System.out.println("Usage: java Exercise21_08 fullfilename");System.exit(1);}String filename = args[0];// Create a tree map to hold words as key and count as valueTreeMap<String, Integer> treeMap = new TreeMap<String, Integer>();try {Scanner input = new Scanner(new File(filename));while (input.hasNext()) {String line = input.nextLine();String[] words = line.split("[ @!~{}\\[\\]$#^&*\n\t\r.,;?'\")(]");for (int i = 0; i < words.length; i++) {if (words[i].trim().length() > 0 &&words[i].trim().matches("[A-Z|a-z]+")) {String key = words[i].toLowerCase();if (treeMap.get(key) != null) {int count = treeMap.get(key);count++;treeMap.put(key, count);}else {treeMap.put(key, 1);}}}}}catch (Exception ex) {ex.printStackTrace();}// Get an entry set for the tree mapSet<Map.Entry<String, Integer>> entrySet = treeMap.entrySet();// Display words in alphabetical orderSystem.out.println("\nDisplay words and their count in " + " ascending order of the words");for (Map.Entry<String, Integer> entry: entrySet)System.out.println(entry.getValue() + "\t" + entry.getKey()); }}21.9import java.util.*;public class Exercise21_09 {public static void main(String[] args) {String[][] stateCapital = {{"Alabama", "Montgomery"},{"Alaska", "Juneau"},{"Arizona", "Phoenix"},{"Arkansas", "Little Rock"},{"California", "Sacramento"},{"Colorado", "Denver"},{"Connecticut", "Hartford"},{"Delaware", "Dover"},{"Florida", "Tallahassee"},{"Georgia", "Atlanta"},{"Hawaii", "Honolulu"},{"Idaho", "Boise"},{"Illinois", "Springfield"},{"Indiana", "Indianapolis"},{"Iowa", "Des Moines"},{"Kansas", "Topeka"},{"Kentucky", "Frankfort"},{"Louisiana", "Baton Rouge"},{"Maine", "Augusta"},{"Maryland", "Annapolis"},{"Massachusettes", "Boston"},{"Michigan", "Lansing"},{"Minnesota", "Saint Paul"},{"Mississippi", "Jackson"},{"Missouri", "Jefferson City"},{"Montana", "Helena"},{"Nebraska", "Lincoln"},{"Nevada", "Carson City"},{"New Hampshire", "Concord"},{"New Jersey", "Trenton"},{"New York", "Albany"},{"New Mexico", "Santa Fe"},{"North Carolina", "Raleigh"},{"North Dakota", "Bismark"},{"Ohio", "Columbus"},{"Oklahoma", "Oklahoma City"},{"Oregon", "Salem"},{"Pennslyvania", "Harrisburg"},{"Rhode Island", "Providence"},{"South Carolina", "Columbia"},{"South Dakota", "Pierre"},{"Tennessee", "Nashville"},{"Texas", "Austin"},{"Utah", "Salt Lake City"},{"Vermont", "Montpelier"},{"Virginia", "Richmond"},{"Washington", "Olympia"},{"West Virginia", "Charleston"},{"Wisconsin", "Madison"},{"Wyoming", "Cheyenne"}};Map<String, String> map = new HashMap<String, String>();for (int i = 0; i < stateCapital.length; i++)map.put(stateCapital[i][0].toLowerCase(), stateCapital[i][1]);Scanner input = new Scanner(System.in);System.out.print("Enter a state: ");String state = input.nextLine().toLowerCase().trim();if (map.containsKey(state))System.out.println("The capital is " +map.get(state));elseSystem.out.println("No such state ");}}21.10import java.util.*;import java.io.*;public class Exercise21_10 {public static void main(String[] args) {// Prompt the user to enter a Java source fileScanner input = new Scanner(System.in);System.out.print("Enter a file name: ");String filename = input.nextLine();// Array of all Java keywords + true + nullString[] keywordString = { "abstract", "finally", "public", "boolean", "float", "return", "break", "for", "short", "byte", "goto", "static","case", "if", "super", "catch", "implements", "switch", "char","import", "synchronized", "class", "instanceof", "this", "const","int", "throw", "continue", "interface", "throws", "default", "long","transient", "do", "native", "try", "double", "new", "void", "else","package", "volatile", "extends", "private", "while", "final","protected", "true", "null" };Set<String> keywordSet = newHashSet<String>(Arrays.asList(keywordString));int count = 0;try {input = new Scanner(new File(filename));String text = "";while (input.hasNext()) {String line = input.nextLine();line = stripLineComments(line);line = stripLineStringLiterals(line);text += line + " ";}text = stripParagraghComments(text);TreeMap<String, Integer> map = new TreeMap<String, Integer>();String[] tokens = text.split("[ \\[,()\\]]");for (String token : tokens) {if (keywordSet.contains(token))if (map.get(token) == null) {map.put(token, 1);} else {int value = map.get(token);value++;map.put(token, value);}}// Get all entries into a setSet<Map.Entry<String, Integer>> entrySet = map.entrySet();// Get key and value from each entryfor (Map.Entry<String, Integer> entry: entrySet)System.out.println(entry.getValue() + "\t" + entry.getKey()); } catch (Exception ex) {ex.printStackTrace();}}/* Strip line comments */private static String stripLineComments(String line) {int index = line.indexOf("//");if (index < 0)return line;elsereturn line.substring(0, index);}/* Strip string literals */private static String stripLineStringLiterals(String line) {int start = line.indexOf("\"");int end = line.indexOf("\"", start + 1);while (start > 0 && end > 0) {line = line.substring(0, start) + line.substring(end + 1);start = line.indexOf("\"");end = line.indexOf("\"");}return line;}/* Strip paragraph comments */private static String stripParagraghComments(String text) {int start = text.indexOf("/*");int end = text.indexOf("*/");while (start > 0 && end > 0) {text = text.substring(0, start) + text.substring(end + 2);start = text.indexOf("/*");。

1. 2. 3. 4.Chapter 1 Introduction to Computers, Programs, and Java A computer is an electronic device that stores and processes data. A computerincludes both hardware and software. In general, hardware is the physical aspect of the computer that can be seen, and software is the invisible instructions that control the hardware and make it work. The hardware of a computer consists of a CPU,cache, memory, hard disk, floppy disk, monitor, printer, and communication devices. The machine language is a set of primitive instructions built into every computer. Assembly language is a low-level programming language in which a mnemonic is used to represent each of the machine language instructions. The high-level languages are English-like and easy to learn and program.The operating system (OS) is a program that manages and controls a computer’s activities. The examples of OS are Windows 98, NT, 2000, XP, or ME. Windows. Application programs such as an Internet browser and a word processor run on top of an operating system.100 in decimal => 64 in hex100 in decimal => 01100100 in binary4340 in decimal => 10F4 in hex4340 in decimal => 1000011110100 in binary2000 in decimal => 7D0 in hex2000 in decimal => 111110100005.1000011001 in binary => 219 in hex1000011001 in binary => 537 in decimal100000000 in binary => 100 in hex 100000000 in binary => 256 in decimal100111 in binary => 27 in hex 100111 in binary => 39 in decimal 6.FEFA9 in hex => 1044393 in decimalFEFA9 in hex => 11111110111110101001 in binary93 in hex => 147 in decimal 93 in hex => 10010011 in binary 2000 in hex => 8192 in decimal7.8.9.10.11.12.13.14.16.17. 2000 in hex => 10000000000000 in binaryDeveloped by a team led by James Gosling at Sun Microsystems in 1991. Originally called Oak, it became Java in 1995 when it was redesigned for developing Internet applications.Java can run on any platform with a Java Virtual Machine. The minimum requirement is the Java Runtime Environment, free from the .The input is the Java source code and the output is the Java bytecode (if compiled successfully).JBuilder by Borland, Sun ONE Studio by Sun, Café by WebGain, Visual Age for Java by IBM are the tools for developing Java programs, not dialects of Java. These tools make developing Java programs easier and more productive.HTML is a markup language for displaying static Web pages. Java is a full-fledged programming language that can be used to develop dynamic Web pages. The Java programs that run from a Web browser are called applets. Java applets must be embedded in HTML files using the <applet> tag.Keywords have specific meaning to the compiler and cannot be used for other purposes in the program such as variables or method names. Examples of keywords are class, static, and void.Java source code is case sensitive. Java keywords are always in lowercase.The source file extension is .java and the bytecode file extension is .class. Comments are used to document what a program is for and how a program is constructed. Comments help the programmers or users to communicate and understand the program. Comments are not programming statements and are ignored by the compiler. In Java, comments are preceded by two forward slashes (//) in a line or enclosed between /* and */ in multiple lines. When the compiler sees //, it ignores all text after // in the same line. When it sees /*, it scans for the next */ and ignores any text between /* and */.15. System.out.println(...);JOptionPane.showMessageDialog(null,“Hello world”);Line 2. Main should be main.Line 2. static is missing.Line 3: Welcome to Java! should be enclosed inside double quotation marks.javac is the JDK command to compile a program program. java is the JDK command to run a program.18.19. Java interpreter cannot find the .class file. Make sure you placed the .class in the right place, and invoked java command with appropriate package name.The class does not have a main method, or the signature of the main method is incorrect.Thank you for evaluating AdreamSoft PDF to Word You can only convert 3 pages with the trial versionTo get all the pages converted, you need to purchase the software from/purchase/buy-pdf-to-word.html。

第一篇基础知识篇本篇主要内容：□第1章 初识Java真面目□第2章 动手写“Hello World”□第3章 扎实Java语言基本语法□第4章 理解算法和流程控制□第5章 流行的Java开发工具□第6章 解密面向对象编程□第7章 初探数组第1章 初识Java真面目Java是Sun Microsystems公司推出的跨多平台、可移植性高的一种面向对象的编程语言。

自面世以来，Java以易学易用、功能强大的特点得到了广泛的应用。

使用Java语言可以编写桌面应用程序、Web应用程序、分布式系统、嵌入式系统应用程序等。

Java语言被誉为是最优秀的计算机语言。

本章注意为读者学习Java作准备，学习本章后，相信读者会爱上Java。

知识点：1、Java是Sun Microsystems公司推出的跨多平台、可移植性高的一种面向对象的编程语言。

2、自面世以来，Java以易学易用、功能强大的特点得到了广泛的应用。

3、使用Java语言可以编写桌面应用程序、Web应用程序、分布式系统、嵌入式系统应用程序等。

4、Java语言被誉为是最优秀的计算机语言。

练习：1、Java是 公司推出的 、 的一种 的编程语言。

2、自面世以来，Java以 、 的特点得到了广泛的应用。

3、使用Java语言可以编写 、 、 、 等。

4、 被誉为是最优秀的计算机语言。

通过本章的学习，希望读者可以达到以下的学习目的：□ 掌握Java语言与其他程序设计语言相比所具有的优势。

□ 了解近几年Java在程序设计语言中的排行。

□ 掌握Java语言的发展史。

□ 了解Java的成功案例。

□ 掌握Java的应用领域。

□ 了解Java程序员的成长之路。

1.1 Java简介首先欢迎大家走进Java世界，来体会一下Java语言带给我们的无限魅力。

在任何一项技术学习之前，都需要先了解这项技术，下面笔者将带领大家一起进入Java世界。

1.1.1 什么是Java语言1995年，Sun公司推出了一种极富创造力的、面向对象的程序设计语言——Java，它由Java 之父詹姆斯·戈士林博士设计。

第一章 Java语言基础 (5)1.1 指出JA V A语言的主要特点和JA V A程序的执行过程。

(5)1.2 说出开发与运行JA V A程序的重要步骤。

(5)1.3 如何区分应用程序和小应用程序？ (5)1.4 说出JA V A源文件的命名规则。

(5)1.6 JA V A语言使用什么字符集？共有多少个不同的字符？ (5)1.7 JA V A语言标识符的命名规则是什么？ (6)1.8 JA V A有那些基本数据类型，它们的常量又是如何书写的？ (6)1.9 指出下列内容哪些是JA V A语言的整型常量，哪些是浮点数类型常量，哪些两者都不是。

(6)第二章运算和语句 (7)2.1 Java的字符能参加算术运算吗？ (7)2.2 占字节多的变量能直接赋值给占字节少的变量么？ (7)2.3 试用Java语言表达式描述以下数学计算式或逻辑条件： (7)2.4 设在求以下表达式之前，整型变量a的值是4，试指出在求了以下表达式之后，变量a、b和c的值。

(7)2.6 若一个数恰好等于它的因子之和，则这个数称为“完全数”。

编写程序求1000之内的所有完全数。

(7)2.7 编写输入正实数x，求平方不超过x的最大整数n，并输出。

(8)2.8 输入正整数n，输出由n行n列星号字符组成的三角形图案。

(11)2.9 设有整型变量x和y的值分别为5和110。

试指出执行了以下循环语句后，变量x和y的值分别多少？ (12)2.10求小于999的所有水仙花数。

(12)2.11 编程序解百鸡问题：鸡翁一，值钱五；鸡母一，值钱三；鸡雏三，值钱一。

百钱买百鸡。

求鸡翁、鸡母和鸡雏各几何？ (13)2.12 编写程序，按下面的公式计算自然对数底e的值:e=1+1/1!+1/2!+1/3!+1/4!+...... (13)2.13 编写程序，用如下公式计算圆周率PI的近似值：PI＝4-4/3+4/5-4/7+4/9-4/11... (14)2.14 回文整数是指正读法和反读相同的整数，编写一个程序，输入一个整数，判断他是否为回文整数。

java语言程序设计基础篇复习题答案【篇一：《java语言程序设计基础教程》(龚永罡—陈昕)习题答案】txt>1.9练习思考题1、a，b，c2、d3、a，b 4 a 5、b6、开发与运行java程序需要经过的三个主要步骤为____ 、校验和___解释执行__ 。

7、如果一个java applet源程序文件只定义有一个类，该类的类名为myapplet，则类myapplet必须是类的子类并且存储该源程序文件的文件名为。

8、如果一个java applet程序文件中定义有3个类，则使用sun 公司的jdk编译器编译该源程序文件将产生3一个文件名与类名相同而扩展名为__class ______________ 的字节码文件。

11、编写一个简单的java应用程序，该程序在命令行窗口输出两行文字：“你好，很高兴学习java”和“we are students”。

解答：class myfirstjava{public static void main(string args[]){system・out.println(“你好，很高兴学习java”)；system.out.println(“we are students”);}}第2章java基本的程序设计结构2.7练习思考题1、a, b, d2、C3、a4、b5、d6、d, f7、b8、d9、d10、a11、D12、a 13、B 14、c15、d16、a17、在java的基本数据类型中，char型采用unicode编码方案，每个unicode码占用字节内存空间，这样，无论是中文字符还是英文字符,都是占用字节内存空间。

18、设x = 2,则表达式( x + + )／3的值是。

19、若x = 5, y = 10,则x y和x = y的逻辑值分别为和。

20、设有数组定义：int myintarray[] = { 10, 20, 30, 40, 50, 60, 70 };则执行以下几个语句后的输出结果是：120。

《Java语言程序设计（基础篇）》（第10版梁勇著）第十九章练习题答案19.1class GenericStack<E> {public final static int INITIAL_SIZE = 16;private E[] elements;private int size;/** Construct a stack with the default initial capacity */public GenericStack() {this(INITIAL_SIZE);}/** Construct a stack with the specified initial capacity */public GenericStack(int initialCapacity) {elements = (E[])new Object[initialCapacity];}/** Push a new element into the top of the stack */public E push(E value) {if (size >= elements.length) {E[] temp = (E[])new Object[elements.length * 2];System.arraycopy(elements, 0, temp, 0, elements.length);elements = temp;}return elements[size++] = value;}/** Return and remove the top element from the stack */public E pop() {return elements[--size];}/** Return the top element from the stack */public E peek() {return elements[size - 1];}/** Exercise03_21 whether the stack is empty */public boolean isEmpty() {return size == 0;}/** Return the number of elements in the stack */public int getSize() {return size;}}19.2public class Exercise19_02 {public static void main(String[] args) {GenericStack<String> stack = new GenericStack<String>();stack.push("Tom");stack.push("George");stack.push("Peter");System.out.println(stack.getSize());System.out.println(stack.peek());System.out.println(stack.pop());System.out.println(stack.peek());}// GenericStack.java: Implementing a stack using inheritance static class GenericStack<E> extends java.util.ArrayList<E> { public boolean isEmpty() {return super.isEmpty();}public int getSize() {return size();}public Object peek() {return get(getSize() - 1);}public Object pop() {Object o = get(getSize() - 1);remove(getSize() - 1);return o;}public Object push(E o) {add(o);return o;}public int search(Object o) {return indexOf(o);}@Overridepublic String toString() {return"stack: " + toString();}}}19.3import java.util.ArrayList;public class Exercise19_03 {public static void main(String[] args) {ArrayList<Integer> list = new ArrayList<Integer>();list.add(14);list.add(24);list.add(14);list.add(42);list.add(25);ArrayList<Integer> newList = removeDuplicates(list);System.out.print(newList);}public static <E> ArrayList<E> removeDuplicates(ArrayList<E> list) { ArrayList<E> result = new ArrayList<E>();for (E e: list) {if (!result.contains(e))result.add(e);}return result;}}19.4public class Exercise19_04 {public static <E extends Comparable<E>> void selectionSort(E[] list) {for (int i = 1; i < list.length; i++) {/** insert list[i] into a sorted sublist list[0..i-1] so thatlist[0..i] is sorted. */E currentElement = list[i];int k;for (k = i - 1; k >= 0 && list[k].compareTo(currentElement) > 0; k--) { list[k + 1] = list[k];}// Insert the current element into list[k+1]list[k + 1] = currentElement;}}}19.5public class Exercise19_05 {public static void main(String[] args) {Integer[] numbers = {1, 2, 3};System.out.println(max(numbers));String[] words = {"red", "green", "blue"};System.out.println(max(words));Circle[] circles = {new Circle(3), new Circle(2.9), new Circle(5.9)};System.out.println(max(circles));}static class Circle implements Comparable<Circle> {double radius;public Circle(double radius) {this.radius = radius;}@Overridepublic int compareTo(Circle c) {if (radius < c.radius)return -1;else if (radius == c.radius)return 0;elsereturn 1;}@Overridepublic String toString() {return"Circle radius: " + radius;}}public static <E extends Comparable<E>> E max(E[] list) { E max = list[0];for (int i = 1; i < list.length; i++) {if (pareTo(list[i]) < 0) {max = list[i];}}return max;}}19.6public class Exercise19_06 {public static void main(String[] args) {Integer[][] numbers = { {1, 2, 3}, {4, 4, 6}};System.out.println(max(numbers));}public static<E extends Comparable<E>> E max(E[][] list) { E max = list[0][0];for (int i = 1; i < list.length; i++) {for (int j = 1; j < list[i].length; j++) {if (pareTo(list[i][j]) < 0) {max = list[i][j];}}}return max;}}19.7public class Exercise19_07 {/** Use binary search to find the key in the list */ public static<E extends Comparable<E>>int binarySearch(E[] list, E key) {int low = 0;int high = list.length - 1;while (high >= low) {int mid = (low + high) / 2;if (pareTo(list[mid]) < 0) {high = mid - 1;}else if (key.equals(list[mid])) {return mid;}else {low = mid + 1;}}return -low - 1; // Now high < low}}19.8import java.util.ArrayList;public class Exercise19_08 {public static void main(String[] args) {ArrayList<Integer> list = new ArrayList<Integer>(); list.add(14);list.add(24);list.add(4);list.add(42);list.add(5);shuffle(list);for (int i = 0; i < list.size(); i++)System.out.print(list.get(i) + " ");}public static <E> void shuffle(ArrayList<E> list) {for (int i = 0; i < list.size() - 1; i++) {int index = (int)(Math.random() * list.size());E temp = list.get(i);list.set(i, list.get(index));list.set(index, temp);}}}19.9import java.util.ArrayList;public class Exercise19_09 {public static void main(String[] args) {ArrayList<Integer> list = new ArrayList<Integer>();list.add(14);list.add(24);list.add(4);list.add(42);list.add(5);Exercise19_09.<Integer>sort(list);System.out.print(list);}/** Sort an array of comparable objects */public static <E extends Comparable<E>> void sort(ArrayList<E> list) { E currentMin;int currentMinIndex;for (int i = 0; i < list.size() - 1; i++) {// Find the minimum in the list[i+1..list.length-2]currentMin = list.get(i);currentMinIndex = i;for (int j = i + 1; j < list.size(); j++) {if (pareTo(list.get(j)) > 0) {currentMin = list.get(j);currentMinIndex = j;}}// Swap list[i] with list[currentMinIndex] if necessary;if (currentMinIndex != i) {list.set(currentMinIndex, list.get(i));list.set(i, currentMin);}}}}19.10import java.util.ArrayList;public class Exercise19_10 {public static void main(String[] args) {ArrayList<Integer> list = new ArrayList<Integer>();list.add(14);list.add(24);list.add(4);list.add(42);list.add(5);System.out.print(max(list));}public static <E extends Comparable<E>> E max(ArrayList<E> list) { E currentMax = list.get(0);for (int i = 1; i < list.size(); i++)if (pareTo(list.get(i)) < 0)currentMax = list.get(i);return currentMax;}}19.11import java.util.ArrayList;public class Exercise19_11 {public static void main(String[] args) {// Create two Complex arrays m1 and m2Complex[][] m1 = new Complex[3][3];Complex[][] m2 = new Complex[3][3];for (int i = 0; i < m1.length; i++)for (int j = 0; j < m1[0].length; j++) {m1[i][j] = new Complex(i + 1, j + 5);m2[i][j] = new Complex(i + 1, j + 6);}// Create an instance of ComplexMatrixComplexMatrix rationalMatrix = new ComplexMatrix();System.out.println("\nm1 + m2 is ");GenericMatrix.printResult(m1, m2, rationalMatrix.addMatrix(m1, m2), '+');System.out.println("\nm1 * m2 is ");GenericMatrix.printResult(m1, m2, rationalMatrix.multiplyMatrix(m1, m2), '*');}public static <E> ArrayList<E> removeDuplicates(ArrayList<E> list) { ArrayList<E> result = new ArrayList<E>();for (E e: list) {if (!result.contains(e))result.add(e);}return result;}}class ComplexMatrix extends GenericMatrix<Complex> {@Override /** Add two rational numbers */protected Complex add(Complex r1, Complex r2) {return r1.add(r2);}@Override /** Multiply two rational numbers */protected Complex multiply(Complex r1, Complex r2) {return r1.multiply(r2);}@Override /** Specify zero for a Complex number */protected Complex zero() {return new Complex(0, 0);}}abstract class GenericMatrix<E> {/** Abstract method for adding two elements of the matrices */ protected abstract E add(E o1, E o2);/** Abstract method for multiplying two elements of the matrices */ protected abstract E multiply(E o1, E o2);/** Abstract method for defining zero for the matrix element */ protected abstract E zero();/** Add two matrices */public E[][] addMatrix(E[][] matrix1, E[][] matrix2) {// Check bounds of the two matricesif ((matrix1.length != matrix2.length) ||(matrix1[0].length != matrix2[0].length)) {throw new RuntimeException("The matrices do not have the same size");}E[][] result =(E[][])new Object[matrix1.length][matrix1[0].length];// Perform additionfor (int i = 0; i < result.length; i++)for (int j = 0; j < result[i].length; j++) {result[i][j] = add(matrix1[i][j], matrix2[i][j]);}return result;}/** Multiply two matrices */public E[][] multiplyMatrix(E[][] matrix1, E[][] matrix2) {// Check boundsif (matrix1[0].length != matrix2.length) {throw new RuntimeException("The matrices do not have compatible size");}// Create result matrixE[][] result =(E[][])new Object[matrix1.length][matrix2[0].length];// Perform multiplication of two matricesfor (int i = 0; i < result.length; i++) {for (int j = 0; j < result[0].length; j++) {result[i][j] = zero();for (int k = 0; k < matrix1[0].length; k++) {result[i][j] = add(result[i][j],multiply(matrix1[i][k], matrix2[k][j]));}}}return result;}/** Print matrices, the operator, and their operation result */ public static void printResult(Object[][] m1, Object[][] m2, Object[][] m3, char op) { for (int i = 0; i < m1.length; i++) {for (int j = 0; j < m1[0].length; j++)System.out.print(" " + m1[i][j]);if (i == m1.length / 2)System.out.print(" " + op + " ");elseSystem.out.print(" ");for (int j = 0; j < m2.length; j++)System.out.print(" " + m2[i][j]);if (i == m1.length / 2)System.out.print(" = ");elseSystem.out.print(" ");for (int j = 0; j < m3.length; j++) System.out.print(m3[i][j] + " ");System.out.println();}}}。