java程序设计基础_陈国君版第五版_第四章习题

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import java.util.Scanner;public class Main4_1 {public static void main(String[] args){Scanner scanner = new Scanner(System.in);float testScore ;char grade ;do{System.out.println("请输入成绩：");testScore = scanner.nextFloat();}while((testScore<0)||(testScore>100));switch((int)testScore/10){case 10 : case 9 : grade = 'A'; break;case 8 : grade = 'B'; break;case 7 : grade = 'C'; break;case 6 : grade = 'D'; break;default: grade = 'E'; break;}System.out.println("本次成绩："+testScore+"\t获得的等级是："+grade);}}

import java.util.Scanner;public class Main4_2{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.print("请输入学生的成绩：");float testScore = scanner.nextFloat();char grade;switch((int)testScore/10){case 10:case 9 : grade = 'A';break;case 8 : if(testScore>=85){grade = 'A';break;} else{grade = 'B';break;}case 7 : grade = 'B';break;case 6 : grade = 'C';break;default: grade = 'D';break;}System.out.println("成绩"+testScore+"的等级是： "+grade);}}

public class Main4_3{public static void main(String[] args){for(int i = 1;i<100;i++){if(i%21==0){System.out.println(i+"\t");}}}}

import java.io.*;public class Main4_4{public static void main(String[] args)throws IOException{BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));System.out.println("请输入一个数：");String str = buf.readLine();int n = Integer.parseInt(str);int sum = 0 ;for(int i = 1;i<=n;i++){int s = 1;for(int j = 1 ; j<=i;j++){s = s*j;}sum += s;}System.out.println("结果为："+sum);}}

import java.util.Scanner;public class Main4_5{public static void main(String[] args){float sum = 0;Scanner scanner = new Scanner(System.in);System.out.println("请输入一个数 n：");int n = scanner.nextInt();for(int i = 1;i<=n;i++){int s =1;for(int j = 1;j <= i ; j++){s = s*j;}sum += Math.pow(-1,i-1)/(float)s;}System.out.println("sum = "+sum);}}

public class Main4_6{public static void main(String[] args){int flag = 0;for(int i = 100; i < 1000; i++){int num1 = i%10;int num2 = (i%100)/10;int num3 = i/100;if(i==(Math.pow(num1,3)+Math.pow(num2,3)+Math.pow(num3,3))){System.out.print(i+"\t");flag++;}if(flag >10){System.out.println();flag = 0;}}}}

import java.io.*;public class Main4_7{public static void main(String[] args)throws IOException{BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));String str ;System.out.println("请输入一个数:");str = buf.readLine();int n = Integer.parseInt(str);int sum = 0;for(int i = 1 ;i < n ; i++){if(n%i==0){sum += i;}}if(sum == n){System.out.println(n+"是一个完全数！");}elseSystem.out.println(n+"不是一个完全数！");}}

import java.io.*;public class Main4_8{public static void main(String[] args)throws IOException{BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));System.out.println("请输入一个整数：");String str = buf.readLine();int n = Integer.parseInt(str);System.out.print(n+"的各位数字之和为");int flag =1;while((n/(int)(Math.pow(10,flag)))!=0){  flag++;}while(flag!=0){System.out.print((int)(n/(Math.pow(10,flag-1))));n %= Math.pow(10,flag-1);flag--;if(flag!=0){System.out.print("+");}}}}

import java.util.Scanner;public class Main4_9{public static void main(String[] args){Scanner scanner = new  Scanner(System.in);System.out.println("请输入一个浮点型数：");float n = scanner.nextFloat();System.out.println(n+"的整数部分为"+(int)n);System.out.println(n+"的小数部分为"+(n-(int)n));}}

public class Main4_10{public static void main(String[] args){float length = 3000;int num = 0;do{length /= 2;num++;}while(length>=5);System.out.println("需要"+num+"天，绳子的长度会短于5米");}}

public class Main4_11{public static void main(String[] args){int n = 5,i=0,j,z;int [][] a = new int [n][n];a[0][0] = 1;for(z = 1 ; z<n;z++){            //z判断有多少行j=0; i = z;                       //哪行开始a[i][j]=a[j][i-1]+1;do{                            //斜向上走 赋值a[i-1][j+1]=a[i][j]+1;i--;j++;}while(j!=z);}for(i=0;i<n;i++){for(j=0;j<(5-i);j++)System.out.print(a[i][j]+"\t");System.out.println();}}}

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