1.编写一个程序，把变量n的初始值设置为1678，然后利用除法运算和取余运算把变量的每位数字都提出来并打印，输出结果为：n=1678n的每位数字是1,6,7,8。

public static void main(String[]args) {
        int n=1678;
        int a,b,c,d;
        a=n%10;
        b=n/10%10;
        c=n/100%10;
        d=n/1000;
        System.out.print(d+" ");
        System.out.print(c+" ");
        System.out.print(b+" ");
        System.out.print(a+" ");


    }
}

 输出结果： 

2.编写Java程序，接受用户输入的1~12之间的整数，若不符合条件则重新输入，利用switch语句输出对应月份的天数。 

public static void main(String[] args) {
        int a = 0;
        Boolean flag = true;
        System.out.println("输入月份弹出天数:");
        Scanner scanner = new Scanner(System.in);
        a = scanner.nextInt();
        if ((a < 1) || (a > 12)) {
            flag = false;
        }

        while (flag == false) {
            System.out.println("输错了再来：");
            a = scanner.nextInt();
            if ((a <= 12) && (a >= 1)) {
                flag = true;

            }

        }

        switch (a) {
            case 1:
                System.out.println("31");
                break;
            case 2:
                System.out.println("28");
                break;
            case 3:
                System.out.println("31");
                break;
            case 4:
                System.out.println("30");
                break;
            case 5:
                System.out.println("31");
                break;
            case 6:
                System.out.println("30");
                break;
            case 7:
                System.out.println("31");
                break;
            case 8:
                System.out.println("31");
                break;
            case 9:
                System.out.println("30");
                break;
            case 10:
                System.out.println("31");
                break;
            case 11:
                System.out.println("30");
                break;
            case 12:
                System.out.println("31");
                break;
        }
    }
}

 输出结果：

 

3.编写一个方法来计算10000以内的素数之和并输出。 

public static void main(String[] args) {
        int b, d = 0;
        for (b = 2; b < 10000; b++) {
            Boolean flag = true;
            for (int i = 2; i < b; i++) {
                if (b % i == 0) {
                    flag = false;
                    break;
                }
            }
            if (flag == true) {
                d = d + b;
            }
        }
        System.out.println("总和为" + d);
    }
}

 输出结果：

4.编写Java程序实现：输入一组整数存放在数组中，比较并输出其中的最大值和最小值；再将数组元素从小到大排序并输出。 

 

import java.util.Arrays;
import java.util.Scanner;

public class fhkjs {
    public static void main(String[] args) {
        int agr[] = new int[5];
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入五个数字：");
        for (int i = 0; i < agr.length; i++) {
            agr[i] = scanner.nextInt();
        }
        int max = agr[0], min = agr[0];
        for (int a = 1; a < agr.length; a++) {
            if (max < agr[1]) {
                max = agr[1];
            }
            if (min > agr[1]) {
                min = agr[1];
            }
        }
        System.out.println("max=" + max + "  min=" + min);
        Arrays.sort(agr);
        for (int i : agr) {
            System.out.println(i + "");
        }
    }
}

输出结果：

 

 5.使用数组存储一个英文句子“Java is an object oriented programming language”。显示该句子，并计算出每个单词的平均字母数。

 public static void main(String[] args) {
        String str="java is an object oriented programming language";
        String[] split=str.split(" ");
        for (int i = 0; i < split.length; i++) {
            System.out.print(split[i]);
            System.out.print(" ");
        }
        System.out.println();
        double res=0;
        for (int i = 0; i < split.length; i++) {
            res+=split[i].length()*1.0/ split.length;
        }
        System.out.println("平均字符长度为：" + res);
    }
}

输出结果：