Java第六次作业

练习

1.使用for循环计算1-100的和，除了以3结尾的那些数

package Second;

public class S1 {

    /**
     * @param args
     */
    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 Second;

public class S2 {

    /**
     * @param args
     */
    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 k = 1; k <= 2 * i - 1; k++) {
                System.out.print("*");
            }
            System.out.println();
        }
        System.out.println();
        System.out.println();
        System.out.println();
        System.out.println();
    }

}

 

 

package Second;

public class S3 {

    /**
     * @param args
     */
    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();
        }

    }
}

 

  3.循环输入学生姓名，直到输入‘Q’程序结束。

package Second;

import java.util.Scanner;

public class S4 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        System.out.println("输入学生的姓名");
        String name = input.next();
        while (name != "Q") {
            name = input.next();
            if (name.equals("Q"))
                break;
        }
        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 Second;

import java.util.Scanner;

public class S5 {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.println("输入学生成绩");
int sum = 0;
for (int i = 1; i <= 5; i++) {
int grade = input.nextInt();
while (grade < 0 || grade > 100) {
System.out.println("输入的成绩无效，请重新输入");
grade = input.nextInt();
break;
}
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 Second;

public class S6 {

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

}

 

 

 

 作业

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”直到猜对位置（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）

 

package Second;

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

public class Zuo1 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        System.out.println("猜个随机数");
        int s = input.nextInt();
        Random r = new Random();
        int a = r.nextInt(99) + 1;
        System.out.println(+a);
        while (a != s) {
            if (s > a) {
                System.out.println("大了点");
            }
            if (s < a) {
                System.out.println("小了点");
            }
            System.out.println("再猜");
            s = input.nextInt();
        }
        System.out.println("猜对了");
    }

}

 

 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）

 

package Second;

import java.util.Scanner;

public class Zuo2 {

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

}

 

  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……

 

package Second;

public class Zuo3 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int a = 1;
        int b = 1;
        int c = 0;
        for (int i = 2; i < 20; i++) {
            c = a + b;
            a = b;
            b = c;
        }
        System.out.println("第20项" + c);
    }

}