java程序设计基础_陈国君版第五版_第四章习题

java程序设计基础_陈国君版第五版_第四章习题

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！");		}else			System.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();		}	}}