第六次作业

1.使用for循环计算1-100的和，除了以3结尾的那些数

package sdsd;

import java.util.Scanner;



public class Test1111 {

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

}

 

2.使用二重循环输出以下图形

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

package sdsd;

import java.util.Scanner;



public class Test1111 {

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

}

 

 *****
****
***
**
*

package sdsd;

import java.util.Scanner;



public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for (int i = 1; i <= 5; i++) {
            for (int j = 1; j <= 6 - i; j++) {
                System.out.print("*");
            }
            System.out.println("\n");
        }
        System.out.println("\n");
    }

}

 

3.循环输入学生姓名，直到输入‘Q’程序结束。

package sdsd;

import java.util.Scanner;

 

public class Test1111 {

public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("输入学生姓名");
Scanner input = new Scanner(System.in);
String name = input.next();
while (name != "Q") {
name = input.next();
if (name.equals("Q"))
System.out.println("程序结束");
}
}
}

 

 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。

 

package sdsd;

import java.util.Scanner;



public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
           int sum=0;
            Scanner input=new Scanner(System.in);
            System.out.println("输入学生成绩");
            for(int i=1;i<=5;i++){
            int grade=input.nextInt();    
            while(grade<0||grade>100){
                System.out.println("输入错误重新输入");
                grade=input.nextInt();
            }
            sum+=grade;        
            }
            System.out.println(sum);
        }
    }

 

5.计算 1+1/（1+2） + 1/（1+2+3） +1/（1+2+3+4）+…………+1/（1+2+....+10）

package sdsd;

import java.util.Scanner;



public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double a = 1;
        double b = 0;
        double sum = 0;
        for (int i = 1; i <= 10; i++) {
            b = b + i;
            sum = sum + a / b;
        }
        System.out.println(sum);
    }
}

 

6.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。

 

package sdsd;

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



public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        Random a = new Random();
        int b = a.nextInt(99);

        int i = 1;
        System.out.println("请猜一个数字(1~99):");
        for (i = 1; i <= 99; i++) {
            int num = input.nextInt();
            if (num > b) {
                System.out.println("大了点");
                continue;
            }
            if (num < b) {
                System.out.println("小了点");
                continue;
            }
            if (num == b) {
                System.out.println("猜对了");
                break;
            }
        }
    }
}

 

7.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）

 

package sdsd;

import java.util.Scanner;

public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        System.out.println("请输入一个数(该数大于1):");
        int num = input.nextInt();
        for (int i = 2; i <= num; i++) {
            if (num % i == 0 && num != i) {
                System.out.println(num + "不为质数，能被" + i + "整除");
                break;
            }

            else {
                System.out.println(num + "为质数！");
                break;
            }
        }
    }
}

 

8.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……

package sdsd;

import java.util.Scanner;

public class Test1111 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
         int a = 1, b = 1, c = 0;
            for (int i = 1; i <= 18; i++) {
                c = a + b;
                a = b;
                b = c;
            }
            System.out.println("裴波那契数列的第20项是:" + c);
    }
}