JAVA第六周作业0409

package com.homework6;
//1.使用for循环计算1-100的和，除了以3结尾的那些数
public class Exe6_1_1 {
    public static void main(String[] args) {
        int sum =0;
        for (int i = 0; i <= 100; i++) {
            if (i %10 ==3) {
                continue;
            }
            sum +=i;
        }
        System.out.println(sum);
    }
}

 

package com.homework6;
/*2.使用二重循环输出以下图形

   *
  ***
 *****
*******


*****
****
***
**
*

*/
public class Exe6_1_2 {
    public static void main(String[] args) {
        for (int i = 1; i <= 4; i++) {
            for (int k = 1; k <= 4-i; k++) {
                System.out.print(" ");
            }
            for (int j = 1; j <= 2*i-1; j++) {
                System.out.print("*");
            }
            System.out.println();
        }
        System.out.println("_____________________________________\n");
        for (int i = 1; i <= 5; i++) {
            for (int j = 1; j <= 6-i; j++) {
                System.out.print("*");
            }            
            System.out.println();
        }
    }
}

 

package com.homework6;
//3.循环输入学生姓名，直到输入‘Q’程序结束。
import java.util.Scanner;

public class Exe6_1_3 {
    public static void main(String[] args) {
        Scanner input =new Scanner(System.in);
        System.out.println("请输入学生姓名:");
        do{
            String name =input.next();
            if (name.equals("Q")) {
                System.out.println("已退出!");
                break;
            }
            System.out.println(name +"\n录入成功，请继续输入,按Q可退出程序");
        }while (true);
    }
}

 

 

package com.homework6;
//4.输入5个学生成绩，求和，当输入不合法的时候，提示输入错误重新输入。
import java.util.Scanner;

public class Exe6_1_4 {
    public static void main(String[] args) {
    Scanner input =new Scanner(System.in);
    int sum =0;
    for (int i = 1; i <= 5; ) {
        System.out.println("请输入第"+i+"个学生成绩:");
        int x =input.nextInt();
        if (x >100 || x <0) {
            System.out.println("输入不合法,请重新输入:");
        }else{
        sum +=x;
        i++;
        }
    }
    System.out.println("成绩总和为:"+sum);
    }
}

 

 

package com.homework6;
//5.计算 1+1/（1+2） +  1/（1+2+3）  +1/（1+2+3+4）+…………+1/（1+2+....+10）
public class Exe6_1_5 {
    public static void main(String[] args) {
        double sum =0;
        int x =0;
        for (int i = 1; i <= 10; i++) {
            x +=i;
            sum +=(1.0/x);
        }
        System.out.println(sum);
    }
}

 

 

package com.homework6;

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

/*1.产生一个1-99的随机数，猜数字，若大了就提示“大了点”，
    若小了就提示“小了点”直到猜对为止。
（判断猜的次数，如果1-3次，提示太棒了  如果5-8次 一般般  如果8次以上 太笨了）*/

public class Exe6_2_1 {
    public static void main(String[] args) {
        Random r = new Random();
        Scanner input = new Scanner(System.in);
        System.out.println("猜数字0~100:");
        int luck = r.nextInt(100);
        int i = 1;
        for (; i <= 100; i++) {
            System.out.println("请输入:");
            int guess = input.nextInt();
            if (luck < guess) {
                System.out.println("大了点!");
            }else if(luck > guess){
                System.out.println("小了点!");
            }else{
                System.out.println("恭喜你,猜对了!");
                break;
            }
        }
        System.out.println(i + "次猜对:");
        if (i <= 3) {
            System.out.println("太棒了!");
        }else if (4 <= i && i<= 6) {
            System.out.println("一般般!");
        }else{
            System.out.println("你太笨了!");
        }
        
    }
}

 

 

package com.homework6;

import java.util.Scanner;

//2.输入一个数，判断是不是质数（只能被1和自身整除的数是质数

public class Exe6_2_2 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入一个数,判断它是不是质数:");
        int luck = input.nextInt();
        boolean r = true;
        if(luck==0||luck==1){
            r = false;
            System.out.println(luck + "不是质数");
        }
        for (int i = 2; i < luck; i++) {
            if(luck %i ==0){
                System.out.println(luck + "不是质数");
                r = false;
                break;
            }
        }
        if (r) {
            System.out.println(luck + "是质数");
        }
    }
}

 

 

package com.homework6;

//3.求裴波那契数列的第20项是什么。裴波那契数列，1,1,2,3,5,8,13，21……

public class Exe6_2_3 {
    public static void main(String[] args) {
        int a=1;
        int b=1;
        int c=2;
        for (int i = 3; i <= 20; i++) {
            c = a+b;
            a = b;
            b = c;
        }
        
        System.out.println("第20项是" + c);
    }
}