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在这里，我选择了几个知识点涉及稍微较多的课后习题进行求解（若有错误，欢迎斧正）

4.1（几何：五边形的面积）

import java.util.Scanner;

public class test4 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input = new Scanner(System.in);
		System.out.println("请输入正五边形中点到顶点的距离：");
		double r=input.nextDouble();
		
		double s=2*r*Math.sin(Math.PI/5);
		System.out.printf("五边形的边长为：%.2f",s);
		
		double area=5*s*s/(4*Math.tan(Math.PI/5));
		System.out.printf("\n五边形的面积为：%.2f",area);
		

	}

}

4.2（最大圆距离）

import java.util.Scanner;

public class test5 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input=new Scanner(System.in);
		System.out.println("Enter point 1（latitude and longitude）in degrees：");
		double pointx1=input.nextDouble();
		double pointy1=input.nextDouble();
		System.out.println("Enter point 2（latitude and longitude）in degrees：");
		double pointx2=input.nextDouble();
		double pointy2=input.nextDouble();
		
		double r=6371.01;
		double d=r*Math.acos(Math.sin(Math.toRadians(pointx1))*Math.sin(Math.toRadians(pointx2))+Math.cos(Math.toRadians(pointx1))*Math.cos(Math.toRadians(pointx2))*Math.cos(Math.toRadians(pointy1-pointy2)));
		System.out.println("The distance between the two points is "+d+" km");
	}

}

4.5（几何：正多边形的面积）

import java.util.Scanner;

public class tset6 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input=new Scanner(System.in);
		System.out.println("Ener the number of sides：");
		int n=input.nextInt();
		System.out.println("Enter the side：");
		double r=input.nextDouble();
		
		double area = n*r*r/(4*Math.tan(Math.PI/n));
		System.out.println("The area of the polygon is "+area);
	}

}

4.6（圆上的随机点）

import java.util.Scanner;

public class test7 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		double r=40;
		double x1,y1,x2,y2,x3,y3;
		double angle1,angle2,angle3,alpha;
		double d1,d2,d3;
		
		//第一个随机点
		alpha=Math.random()*Math.PI*2;
		x1=r*Math.cos(alpha);
		y1=r*Math.sin(alpha);
		
		//第二个随机点
		alpha=Math.random()*Math.PI*2;
		x2=r*Math.cos(alpha);
		y2=r*Math.sin(alpha);
		
		//第三个随机点
		alpha=Math.random()*Math.PI*2;
		x3=r*Math.cos(alpha);
		y3=r*Math.sin(alpha);
		
		d1=Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
		d2=Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
		d3=Math.sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
		
		angle1=Math.toDegrees(Math.acos((d1*d1+d2*d2-d3*d3)/(2*d1*d2)));
		angle2=Math.toDegrees(Math.acos((d1*d1+d3*d3-d2*d2)/(2*d1*d3)));
		angle3=Math.toDegrees(Math.acos((d2*d2+d3*d3-d1*d1)/(2*d2*d3)));
		
		System.out.println("angle1："+angle1+"\nangle2："+angle2+"\nangle3："+angle3);
		
	}

}

4.7（顶点坐标）

//代码1
import java.util.Scanner;

public class test8 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input=new Scanner(System.in);
		System.out.println("Enter the radius of the bounding circle：");
		double r=input.nextDouble();
		
		double x1,y1,x2,y2,x3,y3,x4,y4,x5,y5;
		double alpha,angle2,angle3,angle4,angle5;
		int n=5;
		
		//随机生成一个初始点
		alpha=Math.random()*(2*Math.PI);
		x1=r*Math.cos(alpha);
		y1=r*Math.sin(alpha);
		
		//角度一次加72度即可得到其余四点
		angle2=alpha+Math.PI/n;
		x2=r*Math.cos(angle2);
		y2=r*Math.sin(angle2);
		
		angle3=angle2+Math.PI/n;
		x3=r*Math.cos(angle3);
		y3=r*Math.sin(angle3);
		
		angle4=angle3+Math.PI/n;
		x4=r*Math.cos(angle4);
		y4=r*Math.sin(angle4);
		
		angle5=angle4+Math.PI/n;
		x5=r*Math.cos(angle5);
		y5=r*Math.sin(angle5);
		
		System.out.println("The coordinates of five points on the pentagon are：\n"+x1+" "+y1+"\n"+x2+" "+y2+"\n"+x3+" "+y3+"\n"+x4+" "+y4+"\n"+x5+" "+y5);

	}

}

//代码2
import java.util.Scanner;

public class test8 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input=new Scanner(System.in);
		System.out.println("Enter numer of sides：");
		int n=input.nextInt();
		System.out.println("Enter the radius of the bounding circle：");
		double r=input.nextDouble();
		
		
		double x0,y0,x,y;
		double alpha;
		
		System.out.println("The coordinates of five points on the pentagon are：\\n");
		//随机生成一个初始点
		alpha=Math.random()*(2*Math.PI);
		x0=r*Math.cos(alpha);
		y0=r*Math.sin(alpha);
		
		System.out.println(x0+" "+y0);
		
		for(int i=1;i<n;i++)
		{
			alpha=alpha+Math.PI/n;
			x=r*Math.cos(alpha);
			y=r*Math.sin(alpha);
			System.out.println(+x+" "+y);
		}

	}

}

4.8（给出ASCII码对应的字符）

给出（ASCII码对应的字符）编写一个程序，得到一个ASCII码的输入（0~127之间的一个整数），然后显示该字符

import java.util.Scanner;

public class test9 {

	public static void main(String[] args) {
	Scanner input=new Scanner(System.in);
	System.out.println("Enter an ASCII code：");
	int number=input.nextInt();
	char numchar=(char)number;
	System.out.print("The character for ASCII code "+number+" is "+numchar);

	}

}

4.9（给出字符的Unicode码）

（给出字符的Unicode码）编写一个程序，得到一个字符的输入，然后显示其Unicode值。

import java.util.Scanner;

public class test10 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println("Enter a character：");
		Scanner input=new Scanner(System.in);
		String string=input.next();
		char char1=string.charAt(0);
		int number=(int)char1;
		System.out.println("The Unicode for the character "+char1+" is "+number);
	}

}

4.10（猜测生日）

猜测生日，用户输入字符Y代表‘是’，输入N代表‘不是’，代替之前输入的1和0

import java.util.Scanner;

public class test11 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String set1="1 3 5 7\n"+"9 11 13 15\n"+"17 19 21 23\n"+"25 27 29 31";
		
		String set2="2 3 6 7\n"+"10 11 14 15\n"+"18 19 22 23\n"+"26 27 30 31";
		
		String set3="4 5 6 7\n"+"12 13 14 15\n"+"20 21 22 23\n"+"28 29 30 31";
		
		String set4="8 9 10 11\n"+"12 13 14 15\n"+"24 25 26 27\n"+"28 29 30 31";
		
		String set5="16 17 18 19\n"+"20 21 22 23\n"+"24 25 26 27\n"+"28 29 30 31";
		
		int day=0;
		//Create a Scanner
		Scanner input = new Scanner(System.in);
		
		//prompt the user to anser questions
		System.out.println("Is your birthday in Set1?\n");
		System.out.println(set1);
		System.out.println("\n Enter N for No and Y for Yes：");
		String answer = input.next();
		char answer1=answer.charAt(0);
		
		if(answer1 == 'Y')
			day+=1;
		
		//prompt the user to anser questions
		System.out.println("Is your birthday in Set2?\n");
		System.out.println(set2);
		System.out.println("\n Enter N for No and Y for Yes：");
		answer = input.next();
		answer1=answer.charAt(0);
		
		if(answer1 == 'Y')
			day+=2;
		
		//prompt the user to anser questions
		System.out.println("Is your birthday in Set3?\n");
		System.out.println(set3);
		System.out.println("\n Enter N for No and Y for Yes：");
		answer = input.next();
		answer1=answer.charAt(0);
		if(answer1 == 'Y')
			day+=4;

		//prompt the user to anser questions
		System.out.println("Is your birthday in Set4?\n");
		System.out.println(set4);
		System.out.println("\n Enter N for No and Y for Yes：");
		answer = input.next();
		answer1=answer.charAt(0);
		
		if(answer1 == 'Y')
			day+=8;
		
		//prompt the user to anser questions
		System.out.println("Is your birthday in Set5?\n");
		System.out.println(set5);
		System.out.println("\n Enter N for No and Y for Yes：");
		answer = input.next();
		answer1=answer.charAt(0);
		if(answer1 == 'Y')
			day+=16;
		
		System.out.println("\nYour birthday is："+day+"!");
	}

}

4.12（十六进制转二进制）

编写一个程序，提示用户输入一个十六进制数，显示其对应的二进制数。

import java.util.Scanner;

public class test12 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		char ch;
		String hexString;
		int value,a,b,c,d;
		Scanner input=new Scanner(System.in);
		System.out.print("Enter a hex digit：");
		hexString = input.next();
		ch=hexString.charAt(0);
		if(ch>='A' && ch<='F')
		{
		value=ch-'A'+10;
		System.out.println("The binary value is "+Integer.toBinaryString(value));
		}
		else if(ch>='0' && ch<='9')
		{
			value=ch-'0';
			System.out.println("The binary value is "+Integer.toBinaryString(value));
		}
		else
			System.out.println(ch+" is an invalid input");
	}
		
}

4.15（电话键盘）

电话上的国际标准字母/数字映射

import java.util.Scanner;

public class test13 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String string1;
		char ch;
		int value,number;
		
		Scanner input=new Scanner(System.in);
		System.out.println("Enter a letter：");
		string1=input.next();
		if(string1.length()!=1)
		{
			System.exit(1);
		}
		else {
		ch=string1.charAt(0);
		if(ch>='a' && ch<='z')
		{
			value=ch-'a';
			if(value<='m'-'a')
			{
				number=value/3+2;
			}
			else if(value>='p'-'a' && value<='s'-'a')
				number=7;
			else if(value>='t'-'a' && value<='v'-'a')
				number=8;
			else
				number=9;
			System.out.println("The corresponding number is "+number);
		}
		else if(ch>='A' &&ch<='Z')
		{
			value=ch-'A';
			if(value<='M'-'A')
			{
				number=value/3+2;
			}
			else if(value>='P'-'A' && value<='S'-'A')
				number=7;
			else if(value>='T'-'A' && value<='V'-'A')
				number=8;
			else
				number=9;
			System.out.println("The corresponding number is "+number);
		}
		else
			System.out.println("Enter a letter："+ch+" is an invalid input");
		}
	}

}

4.17（一个月中的日期）

编写一个程序，提示用户输入一个年份和一个月份名称的前三个字母（第一个字母使用大写形式），显示该月中的天数。

import java.util.Scanner;

public class test14 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int year,days=0;
		String string1;
		Scanner input=new Scanner(System.in);
		System.out.println("Enter a year：");
		year = input.nextInt();
		System.out.println("Enter a month：");
		string1=input.next();
		if(string1.equals("Jan") || string1.equals("March")||string1.equals("May")||string1.equals("Jul")||string1.equals("Aug")||string1.equals("Oct")||string1.equals("Dec"))
			days=31;
		else if(string1.equals("Apr")||string1.equals("Jun")||string1.equals("Sep")||string1.equals("Nov"))
			days=30;
		else if(string1.equals("Feb"))
			if((year%4==0 && year%100!=0)||(year%400==0))
				days=29;
			else
				days=28;
		else
			{
			System.out.println("Enter a error");
			System.exit(0);
			}
		System.out.println(days);
	}

}

4.18（学生的专业和状况）

编写一个程序，提示用户输入两个字符，显示这两个字符代表的专业以及状况。第一个字符表示专业，第二个字符表示年级。

• M：数学（Mathematics）
• C：计算机科学（Computer Science）
• I：信息技术（Information technology）
• 1：大一（Freshman）
• 2：大二（Sophomore）
• 3：大三（Junior）
• 4：大四（Senior）

import java.util.Scanner;

public class test15 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String string1,string2="00",string3="00";
		char ch1,ch2;
		Scanner input=new Scanner(System.in);
		System.out.println("Enter two characters：");
		string1=input.next();
		ch1=string1.charAt(0);
		ch2=string1.charAt(1);
		if(ch1=='M')
			string2="Mathematics";
		else if(ch1=='C')
			string2="Computer Science";
		else if(ch1=='I')
			string2="Information technology";
		else
			{
			System.out.print("Invalid input");
			System.exit(1);
			}
		if(ch2=='1')
			string3="Freshman";
		else if(ch2=='2')
			string3="Sophomore";
		else if(ch2=='3')
			string3="Junior";
		else if(ch2=='4')
			string3="Senior";
		else
			{
			System.out.println("Ener error");
			System.exit(1);
			}
		System.out.println(string2+" "+string3);
	}

}

4.21（检查SSN）

编写一个程序，提示用户输入一个社保号码，它的格式是DDD-DD-DDDD，其中D是一个数字。你的程序应该判断输入是否合法

import java.util.Scanner;

public class test16 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String string,string1,string2,string3;
		char ch1,ch2;
		int a,b,c;
		Scanner input=new Scanner(System.in);
		System.out.println("Enter a SSN：");
		string=input.next();
		if(string.length()!=11)
			System.out.println(string+" isn't an invalid social securit number");
		else
		{
			string1=string.substring(0,2);
			a=Integer.parseInt(string1);     //数字字符串变为数值
			ch1=string.charAt(3);
			string2=string.substring(4,5);
			b=Integer.parseInt(string2);     //数字字符串变为数值
			ch2=string.charAt(6);
			string3=string.substring(7,11);  //数字字符串变为数值
			c=Integer.parseInt(string3);
			if(a>0&&a<1000&&b>0&&b<100&&c>0&&c<10000&&ch1=='-'&&ch2=='-')
				System.out.println(string+" is a valid social security number");
			else
				System.out.println(string+" isn't an invalid social securit number");
		}
	}

}

4.23（财务应用：酬金）

import java.util.Scanner;

public class test17 {
	public static void main(String[] args) {
		String employeeName;
		double hoursWorked,hourlyPayRate,federalTaxRate,stateTaxRate;
		
		Scanner input = new Scanner(System.in);
		System.out.print("Enter employee's name: ");
		employeeName = input.nextLine();
		System.out.print("Enter number of hours worked in a week: ");
		hoursWorked = input.nextDouble();
		System.out.print("Enter hourly pay rate: ");
		hourlyPayRate = input.nextDouble();
		System.out.print("Enter federal tax withholding rate: ");
		federalTaxRate = input.nextDouble();
		System.out.print("Enter state tax withholding rate: ");
		stateTaxRate = input.nextDouble();
		
		System.out.printf("Employee Name: %s\n", employeeName);
		System.out.printf("Hours Worked: %.1f\n", hoursWorked);
		System.out.printf("Pay Rate: %.2f\n", hourlyPayRate);
		System.out.printf("Gross Pay: %.2f\n", hoursWorked * hourlyPayRate);
		System.out.printf("Deductions:\n");
		System.out.printf("  Federal Withholding (%.1f%%): $%.2f\n", federalTaxRate * 100, federalTaxRate * hoursWorked * hourlyPayRate);
		System.out.printf("  State Withholding (%.1f%%): $%.2f\n", stateTaxRate * 100, stateTaxRate * hoursWorked * hourlyPayRate);
		System.out.printf("  Total Deduction: $%.2f\n", federalTaxRate * hoursWorked * hourlyPayRate
													+ stateTaxRate * hoursWorked * hourlyPayRate);
		System.out.printf("Net pay: $%.2f\n", hoursWorked * hourlyPayRate
										- federalTaxRate * hoursWorked * hourlyPayRate
										- stateTaxRate * hoursWorked * hourlyPayRate);
		input.close();
	}
}

4.25（生成车牌号码）

假设一个车牌号码由三个大写字母和后面的四个数字组成。编写一个程序，生成一个车牌号码。

public class test18 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		char a,b,c;
		int d;
		a=(char)(Math.random()*25+65);
		b=(char)(Math.random()*25+65);
		c=(char)(Math.random()*25+65);
		d=(int) (Math.random()*10+Math.random()*100+Math.random()*1000+Math.random()*10000);
		System.out.println(""+a+b+c+d);

	}

}

原文链接:https://blog.csdn.net/mynameisgt/article/details/109742798