Java第六次作业

1.使用for循环计算1到100的和，除了结尾为散的那些数。

public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int i;
        int sum=0;
       for( i=1;i<=100;i++){
       if(i%10!=3&i!=3)
       sum+=i;
       
       
    }
       System.out.println(sum);
}
}

2.使用二重循环输出以下图形

public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for(int i=1;i<=4;i++){
            for(int k=3;k>=i;k--){
                System.out.print(" ");
            }
            for(int j=1;j<=2*i-1;j++){
            
                System.out.print("*");
            }
            System.out.print("\n");
        }
       
      
    }
       
}

3.

public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for(int i=5;i>=1;i--){
            
            for(int j=1;j<=i;j++){
            
                System.out.print("*");
            }
            System.out.print("\n");
        }
       
      
    }
       
}

3.循环输入学生姓名，知道输入“q”为止。

import java.util.Scanner;


public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input=new  Scanner(System.in);
    
        int a=0;
        for(;;){
            String name=input.next();
            if(name.equals("q")){
            break;
          
        }
  System.out.println("输入错误；重新输入");
        }
    System.out.println("输入正确");
    }

4.输入五个学生成绩求和。

import java.util.Scanner;


public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input=new  Scanner(System.in);
        Scanner s = new Scanner(System.in);
        int a = 1;
        int sum = 0;
        while(a <= 5){
            System.out.print("输入" + (a) + "号成绩: ");
            int x = s.nextInt();
            if (x >100 || x < 0){
                System.out.println("成绩不合法重新输入");
            }else{
                sum = sum + x;
                a++;
            }
        }

5.计算

import java.util.Scanner;


public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         double sum = 0;
            int j = 0;
            for (int i = 1;i <= 10; i++){
                for (int y = 1; y <= i; y++){
                    j = j + y;
                }
                sum = sum + (1.0/j);
                j = 0;
            }
            System.out.println("sum = " + sum);  
   
    }
    

6.

import java.util.Scanner;
import java.util.Random;

public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Random r = new Random();
        int x = 1 + r.nextInt(100);
        Scanner input = new Scanner(System.in);
        System.out.println("输入1~99的随机数");
        int s = input.nextInt();
        int a = 1;
        while (a >= 1) {
            if (s > x) {
 
                System.out.println("大了点");
                int j = input.nextInt();
                s = j;
                a++;
            } else if (s < x) {
                System.out.println("小了点");
                int j = input.nextInt();
                s = j;
                a++;
            } else {
                a++;
                
            }
        }

7.输入一个数  判断是不是质数

import java.util.Scanner;


public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         Scanner input = new Scanner(System.in);
            System.out.println("输入一个数");
            int a = input.nextInt();
            boolean b = true;
            for (int i = 2; i < a - 1; i++) {
                if (a % i == 0) {
                    b = false;
                    break;
                }
            }
            if (b) {
                System.out.println("是质数");
            } else {
                System.out.println("不是质数");
            }    
    }

8.求裴波那契数列第二十项

import java.util.Scanner;


public class qifei {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         Scanner input = new Scanner(System.in);
            int x = 1;
            int y = 1;
            int z = 0;
            for (int i = 3; i < 21; i++) {
                z = x + y;
                x = y;
                y = z;
            }
            System.out.println("第20项为" + z);
        } 
    }