//程序清单2-1
public class ComputeArea {//功能:实现计算圆面积public static void main(String[] args) {double radius;    //Declare radiusdouble area;    //Declare area//Assign a radiusradius = 20;//Compute Areaarea = radius * radius * 3.14159;//Display resultsSystem.out.println("The area for the circle of radius "+radius + " is " + area);}}//程序清单2-2
import java.util.Scanner;
//功能：从标准输入设备读取Double类型数，实现计算圆面积
public class ComputeAreaWithConsuleInput {public static void main(String[] args) {//Create a Scanner objectScanner input = new Scanner(System.in);//Prompt the user to enter a radiusSystem.out.print("Enter a number for radius: ");double radius = input.nextDouble();//Compute areadouble area = radius * radius * 3.14159;//Display resultSystem.out.println("The area for the circle of radius "+radius + "is " +area);}}//程序清单2-3
//功能：读取三个数值，然后显示它们的平均值import java.util.Scanner;public class ComputeAverage {public static void main(String[] args) {//Create a Scanner objectScanner input = new Scanner(System.in);//Prompt the user to enter three numbersSystem.out.print("Enter three numbers: ");double number1 = input.nextDouble();double number2 = input.nextDouble();double number3 = input.nextDouble();//Compute averagedouble average = (number1 + number2 + number3)/3;//Display resultSystem.out.println("The average of "+ number1  + ""+  number2  + "" +  number3  + " is " + average);  }}//程序清单2-4
//功能：计算一个以秒为单位的时间量所包含的分钟数和剩余秒数的程序
import java.util.Scanner;public class DisplayTime {public static void main(String[] args) {Scanner input = new Scanner(System.in);//提示用户输入System.out.println("Enter an integer for seconds: ");int seconds = input.nextInt();int minutes = seconds / 60; //计算包含的分钟数int remainingSeconds = seconds % 60; //剩余秒数System.out.println(seconds + " seconds is " + minutes +" minutes and "+ remainingSeconds + " seconds");}}//程序清单2-5
//功能：利用公式将华氏温度转换成摄氏温度
import java.util.Scanner;
public class FahrenheitToCelsius {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a degree in Fahrenheit: ");double fahrenheit = input.nextDouble();//Convert Fahrenheit to Celsiusdouble celsius = (5.0 / 9) * (fahrenheit - 32);System.out.println("Fahrenheit " + fahrenheit + " is "+ celsius + "in Celsius");}}//程序清单2-6 ShouCurrentTime.java
//功能：显示当前时间
//说明：本题是开发一个显示当前GMT(格林威治标准时间）的程序；
public class ShowCurrentTime {public static void main(String[] args) {//获得从1970年1月1日0点到当前时间之间单位为毫秒的差值long totalMilliseconds = System.currentTimeMillis();//获取总的秒数long totalSeconds = totalMilliseconds / 1000;//计算当前秒数long currentSecond = totalSeconds % 60;//获取总分钟数long totalMinutes = totalSeconds / 60;//计算当前分钟数long currentMinute = totalMinutes % 60;//获取总的小时数long totalHours = totalMinutes / 60;//计算当前小时数long currentHour = totalHours % 60;//输出结果System.out.println("Current time is " + currentHour + ":"+ currentMinute + ":" + currentSecond + "GMT");}}//程序清单2-8 ComputeLoan.java
import java.util.Scanner;public class ComputeLoan {public static void main(String[] args) {//创建一个Scanner对象Scanner input = new Scanner(System.in);//输入年利率System.out.println("Enter yearly interest rate,for example 8.25:" );double annualInterestRate = input.nextDouble();//获取月利率double monthlyInterestRate = annualInterestRate/1200;//输入年数System.out.println("Enter number of years as an integer,for example 5: ");int numberOfYears = input.nextInt();//输入贷款总数System.out.println("Enter loan amount,for example 120000.95: ");double loanAmount = input.nextDouble();//计算每月贷款支付额和总贷款支付额double monthlyPayment = loanAmount * monthlyInterestRate / (1 - 1 / Math.pow(1+monthlyInterestRate,numberOfYears*12));double totalPayment = monthlyPayment * numberOfYears * 12;//输出计算结果System.out.println("The monthly payment is " + (int)(monthlyPayment * 100)/100.0);System.out.println("The total payment is " + (int)(totalPayment * 100)/100.0);}}//程序清单2-9 DisplayUnicode.java
//程序功能：显示两个中文字符和三个希腊字母
import javax.swing.JOptionPane;public class DisplayUnicode {public static void main(String[] args){JOptionPane.showMessageDialog(null, "\u6B22\u8FCE \u03b1\u03b2\u03b3","\u6B22\u8FCE welcome",JOptionPane.INFORMATION_MESSAGE);}}//程序清单2-10
//程序功能：整钱兑零
import java.util.Scanner;public class ComputeChange {public static void main(String[] args){//创建一个ScannerScanner input = new Scanner(System.in);//从控制台输入钱数System.out.print("Enter an amount in double, for example 11.56: ");double amount = input.nextDouble();//引入变量remainingAmount来存储变化的余额int remainingAmount = (int)(amount * 100); //将钱数转换为1分币的个数//求出1美元的个数int numberOfOneDollars = remainingAmount / 100;remainingAmount = remainingAmount % 100;//求出2角5分币的个数int numberOfQuarters = remainingAmount / 25;remainingAmount = remainingAmount % 25;     //剩余1分币的个数//求出1角币的个数int numberOfDimes = remainingAmount / 10;remainingAmount = remainingAmount % 10;      //剩余1分币的个数//求出5分币的个数int numberOfNickles = remainingAmount / 5;remainingAmount = remainingAmount % 5;      //剩余1分币的个数//一分币的个数int numberOfPennies = remainingAmount;//输出结果System.out.println("Your amount " + amount + " consist of \n"+"\t" + numberOfOneDollars + " dollars\n" +"\t" + numberOfQuarters + " quarters\n" +"\t" + numberOfDimes + " dimes\n" +"\t" + numberOfNickles + " nickles\n" +"\t" + numberOfPennies + " pennies");}}//程序清单2-11 ComputeLoanUsingInputDialog.java
import javax.swing.JOptionPane;public class ComputeLoanUsingInputDialog {public static void main(String[] args){//Enter yearly interest rateString annualInterestRateString = JOptionPane.showInputDialog("Enter yearly interest rate,for example 8.25: ");//Covert string to doubledouble annualInterestRate =Double.parseDouble(annualInterestRateString);//Obtain monthly interest ratedouble monthlyInterestRate = annualInterestRate / 1200;//Enter number of yearsString numberOfYearString = JOptionPane.showInputDialog("Enter numbers of years as an integer, \nfor example 5: ");//Convert string to intint numberOfYears = Integer.parseInt(numberOfYearString);//Enter loan amountString loanString = JOptionPane.showInputDialog("Enter loan amount,for example 120000.95:");//Convert String to doubledouble loanAmount = Double.parseDouble(loanString);//Calclate payment double monthlyPayment = loanAmount * monthlyInterestRate / (1- 1/ Math.pow(1 + monthlyInterestRate, numberOfYears * 12));double totalPayment = monthlyPayment * numberOfYears *12;//Format to keep two digits after the decimal pointmonthlyPayment = (int)(monthlyPayment * 100) / 100.0;totalPayment =(int)(totalPayment * 100) / 100.0;//Display resultsString output = "The monthly payment is " + monthlyPayment +"\nThe total payment is " + totalPayment;JOptionPane.showMessageDialog(null,output);}}