Java程序语言（基础篇）第2章 基本程序设计 编程练习题解答

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 //编程练习题2.1~2.25/** * 2.1 程序要求：编写程序，从控制台读入double型的摄氏温度，然后将其转换为华氏温度，并且显示结果。 * 转换公式如下所示： * fahrenheit = (9/5) * celsius +32 (华氏度= （9/5） * 摄氏度+32) * @作者：wwj * 日期：2012/5/6 * 功能：将摄氏温度转换为华氏温度 *  * 运行结果： * Enter a degree in Celsius: 43 * 43.0 Celsius is 109.4 Fahrenheit */import java.util.Scanner;public class Exercise2_1 { public static void main(String[] args) {  Scanner input = new Scanner(System.in);    //输入一个摄氏温度  System.out.println("Enter a degree in Celsius: ");  double celsius = input.nextDouble();    //转换为华氏温度  double fahrenheit = (9.0/5) * celsius + 32;    //输出结果  System.out.println(celsius + " Celsius is " + fahrenheit + " Fahrenwheit");   }}//Exersise2_2.java/** * 程序要求：读入圆柱体的半径和高，并使用下列公式计算圆柱的体积： *    面积=半径 x 半径 x π *     体积= 面积 x 高 * 作者：wwj * 功能：计算圆柱体的体积 *  * 运行结果： * Enter the radius and length of a cylinder: 5.5 12 * The area is 95.0331 * The volume is 1140.4 */import java.util.Scanner;public class Exercise2_2 { public static void main(String[] args) {  final double PI = 3.14159;  Scanner input = new Scanner(System.in);    //输入半径和高  System.out.println("Enter the radius and length of a cylinder: ");  double radius = input.nextDouble();  double height = input.nextDouble();    //计算面积和体积  double area = radius * radius * PI;  double volume = area * height;    //输出结果  System.out.println("The area is " + area);  System.out.println("The volume is " + volume); }}//Exercise2_3.java/** *  * 程序要求：编写程序，读入英尺数，将其转换为米数并显示结果。一英尺等于0.305米。 *  * 作者：wwj * 日期：2012/5/8 *  * 运行结果示例： * Enter a value for feet: 16 * 16 feet is 4.88 meters */import java.util.Scanner;public class Exercise2_3 { public static void main(String[] args) {  final double ONE_FEET = 0.305;  Scanner input = new Scanner(System.in);    //读入英尺数  System.out.println("Enter a value for feet:");  double feet = input.nextDouble();    //转换结果  double meter = feet * ONE_FEET;    //输出  System.out.println(feet + " feet is "+ meter + " meters ");     }}//Exercise2_4.java/** *  * 程序要求：编写程序，将磅数转换为千克数。程序提示用户输入磅数，然后转换车成千克并显示结果。 * 一磅=0.454千克。 *  * 作者:wwj * 日期：2012/5/8 *  * 运行结果示例： * Enter a number in pounds: 55.5 * 55.5 pounds is 25.197 kilograms *  */import java.util.Scanner;public class Exercise2_4 { public static void main(String[]args){  Scanner input = new Scanner(System.in);  final double ONE_POUND = 0.454;    //提示输入磅数  System.out.println("Enter a number in pounds: ");  double pounds = input.nextDouble();    //将磅数转换为千克数  double kilograms = pounds * ONE_POUND;    //输出结果  System.out.println(pounds + " pounds is " + kilograms + " kiligrams"); }}//Exercise2_5.java/** *  * 程序要求：读入一笔费用与酬金率，计算酬金和总钱数。例如，如果用户输入10作为费用，15%作为酬金率， * 计算结果显示酬金$1.5,总费用$11.5. *  * 作者：wwj * 日期：2012/5/8 * 功能：计算小费 *  * 运行结果示例： * Enter the subtotal and a gratuity rate: 15.69 15 * The gratuity is 2.35 and total is 18.04 *  */import java.util.Scanner;public class Exercise2_5 { public static void main(String[] args) {  Scanner input = new Scanner(System.in);    //读入一笔费用和酬金率  System.out.println("Enter the subtotal and a gratuity rate: ");  double subtotal = input.nextDouble();  double rate = input.nextDouble() * 0.01;    //计算酬金和总费用  double gratuity = subtotal * rate;  double totalMoney = subtotal + gratuity;    //输出结果  System.out.println("The gratuity is " + gratuity + " and total is "+ totalMoney);   }}//Exercise2_6.java/** *  * 程序要求：读取一个在0到1000之间的整数，并将该整数的各位数字相加。 * 例如：整数是932，各位数字之和为14。 *  * 作者：wwj * 日期：2012/5/8 * 功能：求一个整数各位数之和 *  * 运行结果示例： * Enter a number between 0 and 1000:999 * The sum of the digits is 27 */import java.util.Scanner;public class Exercise2_6 { public static void main(String[] args){  Scanner input = new Scanner(System.in);  int sum;    //输入一个数字  System.out.println("Enter a number between 0 and 1000: " );  int num = input.nextInt();    //分解数字   if(num <= 99){     int num1 = num % 10;   int num2 = num / 10;   sum = num1 + num2;  }  else {   int num1 = num % 10;  //个位数   int num2 = num % 100 / 10; //十位数   int num3 = num / 100;  //百位数   sum = num1 + num2 + num3;  }      //输出结果  System.out.println("The sum of the digits is " + sum); }}//Exercise2_7.java/** *  * 程序要求：编写程序，提示用户输入分钟数（例如十亿）然后显示这些分钟数代表多少年和多少天 * 为了简化问题，假设一年又365天。 *  * 作者：wwj * 日期：2012/5/8 * 功能：求出年数 *  * 运行结果示例： * Enter the number of minutes: 1000000000 * 1000000000 minutes is approximately 1902 years and 214 days. */import java.util.Scanner;public class Exercise2_7 { public static void main(String[]args){  Scanner input = new Scanner(System.in);  final int ONEYEAR_OF_MINUTES = 365 * 60 * 24;  final int ONEDAY_OF_MINUTES = 60 * 24;    //输入分钟数  System.out.println("Enter the number of minutes:");  int  minutes = input.nextInt();    //计算年数和天数  int numOfYears = minutes / ONEYEAR_OF_MINUTES;  int numOfDays = (minutes % ONEYEAR_OF_MINUTES) / ONEDAY_OF_MINUTES;    //输出年数和天数  System.out.println(minutes + " minutes is approximately " + numOfYears + " years "    + numOfDays + " days");     } }//Exercise2_8.java/** *  * 程序要求：编写程序接收一个ASCII码（从0到128的整数），然后显示它代表的字符。 * 例如，如果用户输入的是97，程序显示的是字符a。 *  * 作者：wwj * 日期：2012/5/8 * 功能：求ASCII码对应的字符 *  * 运行结果示例： * Enter an ASCII code:69 * The character for ASCII code 69 is E */import java.util.Scanner;public class Exercise2_8 { public static void main(String[]args){  Scanner input = new Scanner(System.in);      //输入ASCII码  System.out.println("Enter an ASCII code:");  int ascii_code = input.nextInt();    //转换为对应字符  char character = (char)ascii_code;    System.out.println("The character for ASCII code " + ascii_code + " is " + character);   }}//Exercise2_9.java/** *  * 程序要求：改写程序清单2-10，解决将double型值为int型值时可能会造成精度损失的问题。 * 输入的输入值是一个整数，其最后两位代表是分币值。例如：1156就表示的是11美元56美分 *  * 作者：wwj * 日期：2012/5/8 * 功能：整钱兑零 */import java.util.Scanner;public class Exercise2_9 { public static void main(String[] args){  //创建一个Scanner对象  Scanner input = new Scanner(System.in);    //输入总钱数  System.out.print("Enter an amount,for example 1156: ");  int amount = input.nextInt();    //找出1美元的个数  int numberOfOneDollars = amount / 100;  amount = amount % 100;    //找出2角5分币的个数  int numberOfQuarters = amount / 25;  amount = amount % 25;    //找出1角币的个数  int numberOfDimes = amount / 10;  amount = amount % 10;    //找出5分币的个数  int numberOfNickles = amount /5;  amount = amount % 5;    //找出1分币的个数  int numberOfPennies = amount;    //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");  }}//Exercise2_10.java/** *  * 程序要求：使用图形用户界面输入 * 改写程序清单2-10，使用图形用户界面输出 *  * 作者：wwj * 日期：2012/5/8 * 功能：整钱兑换 *  */import javax.swing.JOptionPane;public class Exercise2_10 { public static void main(String[] args){  //输入总钱数  String amountString = JOptionPane.showInputDialog(    "Enter an amount for example 1156:");    int amount = Integer.parseInt(amountString);    int numberOfOneDollars = amount / 100; //美元  int numberOfPennies = amount % 100; //美分    String output = "Your amount " + amount + " consist of \n" +   "\t" + numberOfOneDollars + " dollars\n" +  "\t" + numberOfPennies + " pennies";    //输出兑零后的结果  JOptionPane.showMessageDialog(null, output); }}import javax.swing.JOptionPane;//Exercise2_11.java/** * 2.11 程序要求：编写程序，读入下列信息并打印工资单 * 雇员的名字(例如Smith) * 每周的工作小时数(例如10) * 每小时工资(例如6.75) * 联邦所得税税率(例如20%) * 州所得税税率(例如9%) * 作者：wwj * 日期：2012/5/17 * 功能：计算工资单 */public class Exercise2_11 { public static void main(String[] args){  //输入对话框：雇员的名字  String empName = JOptionPane.showInputDialog(    "Enter employee's name,for example Smith");  //输入对话框：每周的工作小时数  String empHoursString = JOptionPane.showInputDialog(    "Enter number of hours worked in a week:");  //将string类型的工作小时数转换为double类型  double empHours = Double.parseDouble(empHoursString);  //输入对话框：每小时工资  String empHourSalaryString = JOptionPane.showInputDialog(    "Enter hourly pay rate:");  //将string类型的工资转换为double类型  double empHourSalary = Double.parseDouble(empHourSalaryString);  //输入对话框：联邦所得税税率  String fedaralRateString = JOptionPane.showInputDialog(    "Enter federal tax withholding rate:");  //将string类型税率转换为double类型  double federalRate = Double.parseDouble(fedaralRateString);  //输入对话框：州所得税税率  String stateRateString = JOptionPane.showInputDialog(    "Enter state tax withholding rate:");  double stateRate = Double.parseDouble(stateRateString);  double grossPay = empHourSalary * empHours;  double federalRatePay = grossPay * federalRate;  double stateRatePay = grossPay * stateRate;  double totalDeduction = federalRatePay + stateRatePay;  //打印结果  String output  = "Employee Name: " + empName +      "\nHour Worked: " + empHours +       "\nPay Rate: " + empHourSalary +       "\nGross Pay: " + grossPay +      "\nDeductions:\n" +       "  Federal Withholding(" + federalRate + "):"+ federalRatePay+       "\n State Withholding(" + stateRate + "):"+ stateRatePay +      "\n Total Deduction" + totalDeduction + "";  JOptionPane.showMessageDialog(null, output);     }}import java.util.Scanner;/** * 2.12 程序要求：如果你知道收支余额和年利率的百分比，你就可以是使用下面的公式计算下个月要支付的利息额： * 利息额=收支余额 x （年利率/1200） * @author wwj * */public class Exercise2_12 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //请输入收支余额和年利率  System.out.println("Enter balance and interest rate(e.g., 3 for 3%):" );  double balance = input.nextDouble();  double interestRate = input.nextDouble();    //计算下个月要支付的利息额  double interest = balance * (interestRate / 1200);    //输出结果  System.out.println("The interest is:" + interest);    }}import java.util.Scanner;/** * 2.13 程序要求：编写程序，读取投资总额、年利率和年数，然后使用下面的公式显示未来的投资金额： * futureInvestmentValue = investmentAmount * (1 + annuallyInterestRate)^(numberOfYears*12) * @author wwj * */public class Exercise2_13 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //读取投资总额  System.out.print("Enter investment amount:");  int investment = input.nextInt();  //读取年利率  System.out.print("Enter monthly interest rate:");  double rate = input.nextDouble();  //读取年数  System.out.print("Enter number of years:");  int years = input.nextInt();    //计算未来的投资金额  double futureInvestmentValue = investment * Math.pow(1 + rate, years * 12);    //显示结果  System.out.println("Accumulated value is:" + futureInvestmentValue);     }import java.util.Scanner;/** * 2.13 程序要求：编写程序，读取投资总额、年利率和年数，然后使用下面的公式显示未来的投资金额： * futureInvestmentValue = investmentAmount * (1 + annuallyInterestRate)^(numberOfYears*12) * @author wwj * */public class Exercise2_13 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //读取投资总额  System.out.print("Enter investment amount:");  int investment = input.nextInt();  //读取年利率  System.out.print("Enter monthly interest rate:");  double rate = input.nextDouble();  //读取年数  System.out.print("Enter number of years:");  int years = input.nextInt();    //计算未来的投资金额  double futureInvestmentValue = investment * Math.pow(1 + rate, years * 12);    //显示结果  System.out.println("Accumulated value is:" + futureInvestmentValue);     }import java.util.Scanner;/** * 2.14 程序要求：计算BMI（身体质量指数），它的值可以通过将体重（以公斤为单位）除以身高（以米为单位） * 的平方值得到。编写程序，提示用户输入体重（以磅为单位）以及身高（以米为单位），然后显示BMI * @author Administrator * */public class Exercise2_14 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //输入体重  System.out.print("Enter weight in pounds :");  double weight = input.nextDouble() * 0.45359237;  //输入身高  System.out.print("Enter height in inches :");  double height = input.nextInt() * 0.0254;    //计算BMI  double BMI = weight / Math.pow(height, 2);    //显示BMI  System.out.println("BMI is:" + BMI); }}import java.util.Scanner;/** * 2.15 程序要求：假设你每月向银行账户存100美元，年利率为5%，那么每月利率是0.05/12=0.00417. * 第一个月之后，账户上的值就变成：100 * (1 + 0.00417) = 100.417 * 第二个月之后，账户上的值就变成：(100 + 100.417) * (1+ 0.00417) = 201.252 * 第三个月之后，账户上的值就变成：(100 + 201.252) * (1+ 0.00417) = 302.507 * 依此类推。 * 编写程序显示六个月之后账户上的钱数。 * @author wwj * */public class Exercise2_15 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    int annuallyMonthDollar = 100;  double interestRate = 0.05 / 12.0;    //1~6月份账户的值  double firstMonthAcount = annuallyMonthDollar * (1 + interestRate);  double secondMonthAcount = (annuallyMonthDollar + firstMonthAcount) * (1 + interestRate);  double thirdMonthAcount = (annuallyMonthDollar + secondMonthAcount) * (1 + interestRate);  double forthMonthAcount = (annuallyMonthDollar + thirdMonthAcount) * (1 + interestRate);  double fifthMonthAcount = (annuallyMonthDollar + forthMonthAcount) * (1 + interestRate);  double sixthMonthAcount = (annuallyMonthDollar + fifthMonthAcount) * (1 + interestRate);    //显示六月后账户的值  System.out.println("sixthMonthAcount is " + sixthMonthAcount);   }}import java.util.Scanner;/** * 2.16 程序要求：编写程序，计算将水从初始温度加热到最终温度所需的能量。 * 计算能量的公式是： *    Q = M * (最终温度 - 初始温度) * 4184 * 这里的M是千克为单位的水的重量，温度以摄氏度为单位，而能量Q以焦耳为单位。 * @author wwj * */public class Exercise2_16 { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Scanner input = new Scanner(System.in);    //输入水的重量  System.out.print("Enter the amount of water in kilograms:");  double M = input.nextDouble();  //输入初始温度  System.out.print("Enter the initial temperature:");  double initialTemp = input.nextDouble();  //输入最终温度  System.out.print("Enter the final temperature:");  double finalTemp = input.nextDouble();    double Q = M * (finalTemp - initialTemp) * 4184;  System.out.println("The energy needed is :" + Q);   }}import java.util.Scanner;/** * 2.17 程序要求：计算风寒温度，计算公式如下： * t=35.74 + 0.6215 * t' - 35.75 * v^0.16 + 0.4275 * t' * v^0.16 * 这里的t’是室外温度，以华摄氏度为单位，而v是速度，以每小时英里数为单位。t是风寒温度。 * 该公式不适用于风速低于2mph或温度在-58F以下或41F以上的情况。 * @author wwj * */public class Exercise2_17 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //输入室外的温度  System.out.print("Enter the temperature in Fahrenheit: ");  double temp = input.nextDouble();  //输入风速  System.out.print("Enter the wind speed miles per hours: ");  double wSpeed = input.nextDouble();    //计算风寒温度  double t = 35.74 + 0.6215 * temp - 35.75 * Math.pow(wSpeed, 0.16) + 0.4275 * temp * Math.pow(wSpeed, 0.16);    //显示结果  System.out.println("The wind chill index is " + t); }   }/** * 2.18 程序要求：打印表格，显示下面的表格： * a b pow(a,b) * 1 2 1 * 2 3 8 * 3 4 81 * 4 5 1024 * 5 6 15625 * @author wwj * */public class Exercise2_18 { public static void main(String[] args){  int a,b;  int n = 5;  System.out.println("a     b     pow(a,b)");  for (int i = 1; i <= n; i++){   a = i;   b = i + 1;   System.out.println(a + "     " + b + "     " + Math.pow(a,b));  } }}/** * 2.19 编写程序，使用System.CurrentTimeMillis()显示任意一个大写字母 * @author wwj * */public class Exercise2_19 { public static void main(String[] args){  long time = System.currentTimeMillis();  int num = (int)(time % 25) + 65;  System.out.println((char)num);   }}import java.util.Scanner;/** * 2.20 程序要求：编写程序，提示用户输入两个点(x1,y1)和(x2,y2)然后显示两点间的距离。 * 计算两点间距离的公式是sqrt(Math.pow(x2-x1,2)+Math.pow(y2-y2,2)). * @author Administrator * */public class Exercise2_20 { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Scanner input = new Scanner(System.in);    //输入第一个点  System.out.println("Enter x1 and y1:");  double x1,y1;  x1 = input.nextDouble();  y1 = input.nextDouble();  //输入第二个点  System.out.println("Enter x2 and y2");  double x2,y2;  x2 = input.nextDouble();  y2 = input.nextDouble();    //计算两点间距离  double distance = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));  //显示结果  System.out.println("The distance of the two points is:" + distance); }}import java.util.Scanner;/** * 2.21 程序要求：编写程序，提示用户输入三角形的三个点(x1,y1)、(x2,y2)、(x3,y3) * 然后显示它的面积。计算三角形面积的公式是： * s = (side1 + side2 + side3)/2 * area= sqrt(s(s-side1)(s-side2)(s-side3)) * @author Administrator * */public class Enxecise2_21 { public static void main(String[] args){  Scanner input = new Scanner(System.in);    //输入三个点  System.out.print("Enter three points for a triangle：");  double x1,x2,x3,y1,y2,y3;  x1 = input.nextDouble();  y1 = input.nextDouble();  x2 = input.nextDouble();  y2 = input.nextDouble();  x3 = input.nextDouble();  y3 = input.nextDouble();    //计算三角形面积  double side1 = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));  double side2 = Math.sqrt(Math.pow(x3 - x2, 2) + Math.pow(y3 - y2, 2));  double side3 = Math.sqrt(Math.pow(x1 - x3, 2) + Math.pow(y1 - y3,2));  double s = (side1 + side2 + side3) / 2;  double area = Math.sqrt(s * (s - side1) * (s - side2) * (s - side3) );    //显示结果  System.out.println("The area of the triangle is :" + area); }}import java.util.Scanner;/** * 2.22 程序要求：编写程序，提示用户输入六边形的边长，然后显示它的面积。 * 计算六边形面积的公式： * area =( 3 * sqrt(3) * s^2 )/ 2 * @author Administrator * */public class Exercise2_22 { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Scanner input = new Scanner(System.in);    //输入六边形的边长  System.out.print("Enter the side:" );  double side = input.nextDouble();    //计算面积  double area =( 3 * Math.sqrt(3) * side * side)/2;    //显示结果  System.out.println("The area of the hexagon " + area); }}import java.util.Scanner;/** * 2.23 程序要求：平均加速度定义为速度的变化量除以这个变化所用的时间，如下式： * a = (v1 - v0) / t * @author wwj * */public class Exercise2_23 { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Scanner input = new Scanner(System.in);    //输入起始速度、终止速度、时间段  System.out.print("Enter v0,v1,and t:");  double v0 = input.nextDouble();  double v1 = input.nextDouble();  double t = input.nextDouble();    //计算加速度  double a = (v1 - v0) / t;    //显示加速度  System.out.println("The average acceleration is :" + a); }}import java.util.Scanner;/** * 2.24 程序要求：假设一个飞机的加速度是a而起飞速度是v，那么飞机起飞所需要的最短跑道长度 * length = v^2 / 2*a * 编写程序，提示用户输入以米/秒为单位的速度v和以米/秒的平方为单位的加速度a，然后显示最短跑道长度 * @author wwj * */public class Exercise2_24 { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  Scanner input = new Scanner(System.in);    //输入v和a  System.out.print("Enter v and a:");  double v = input.nextDouble();  double a = input.nextDouble();  //计算跑道长度  double length = Math.pow(v,2)/( 2 * a);    //显示结果  System.out.println("The minimum runway length for this airplaneis :" + length); }}

           

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