1 求指定两个数的最大公约数和最小公倍数

    public static void main(String[] args) {
    
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入第一个数");
        int num1 = scanner.nextInt();
        System.out.print("请输入第二个数");
        int num2 = scanner.nextInt();
        int bigNum = Math.max(num1, num2);
        int smallNum = Math.min(num1, num2);
        int commDivisor = 0;
        for (int i = 1; i < bigNum; i++) {
    
            if ( bigNum % i == 0 && smallNum % i == 0) {
    
                if ( i > commDivisor )
                    commDivisor = i;
            }
        }
        System.out.println("最大公约数为："+commDivisor);

        for (int i = bigNum; i > 0; i++) {
    
            if ( i % num1 == 0 && i% num2 ==0){
    
                System.out.println("最小公倍数为：" + i);
                break;
            }
        }
    }

2. 打印100以内除了尾数为3,5,7的所有数

	public static void main(String[] args){
    
        for (int i = 1; i <= 100; i++) {
    
            int count = 0;
            int j = i;
            while (j >= 1)
            {
    
                j /= 10;
                count++;
            }
            switch (count){
    
                case 1 -> {
    
                    if( i == 3 || i == 5 || i == 7)
                                continue;
                }
                case 2 -> {
    
                    if( i % 10 == 3 || i % 10 == 5 || i %10 == 7)
                        continue;
                }
            }
            System.out.println(i);
            //System.out.println("此数是"+ count + "位数");
        }
    }

3.接收用户输入的数字,判断在此范围内质数的个数，例如输 入90，输出0-90以内的所有质数的数量

	public static void main(String[] args){
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入范围");
        int N = scanner.nextInt();
        for (int i = 1; i <= N; i ++){
    
            boolean flag = true;
            for (int j = 2 ; j <= i;j ++){
    
                if( i % j == 0 & j !=i)//判断此数不是素数
                {
    
                    flag = false;
                    break;
                }
            }
            if (flag)
                System.out.println( i + "是素数");
        }
    }

4.洪乞丐干10天，收入是多少？

天朝有一个乞丐姓洪，去天桥要钱 第一天要了1块钱 第二天要了2块钱 第三天要了4块钱 第四天要了8块钱 以此类推

	public static void BeggerHong(String[] args){
    
        int sum = 0;
        int dayPay = 1;
        for (int i = 1; i < 10; i++) {
    
            dayPay *= 2;
            sum += dayPay;
        }
        System.out.println("BeggerHong 10天挣了" + sum + "块钱");
    }

5. 李四跑步

李四每天跑步 第一周周一跑 100 米，周二到周天每天比前一天多 100 米。 往后每周以比前一周周一多 100 米。 请问 李四 n（控制台输入） 天后跑了多少米

	public static void RunnerLi(String[] args){
    
        int searchDay = 10;
        int week = searchDay / 7;
        int monday = 0;
        int distance = 0;
        for (int i = 0; i < week; i++) {
    
            monday += 100;
            int dayRunDis = monday;
            for (int j = 1; j <= 7; j++) {
    
                distance += dayRunDis;
                dayRunDis += 100;
            }
        }
        int dayRunDis = monday + 100;
        for (int i = 0; i < searchDay % 7; i++) {
    
                distance += dayRunDis;
                dayRunDis += 100;
        }
        System.out.println(distance);
    }

6.计算 n 的阶乘

5! = 5 * 4 * 3 * 2 * 1 输入一个数，计算阶乘

public static void main(String[] args) {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入一个数，计算其阶乘");
        int num = scanner.nextInt();
        int factorial = 1;
        for (int i = 1; i <= num ; i++) {
    
            factorial *= i;
        }
        System.out.println(factorial);
    }

7.输入一个数字，和位数，判断这个数是否回文数字1221 就 是回文数字

public static void main(String[] args) {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入一个四位数");
        int num = scanner.nextInt();
        int frs = num / 1000;
        int sec = num / 100 % 10;
        int srd = num / 10 % 10;
        int frt = num % 10;
        if ( frs == frt )
        {
    
            if (sec == srd)
            {
    
                System.out.println("此数是回文数");
            }
        }
        else System.out.println("此数不是回文数");
    }

8. 输入行数 显示如图所示的空心三角形

public static void main(String[] args) {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入三角形的边长");
        int H = scanner.nextInt();
        for (int i = 0; i < H-1; i++) {
    
            for (int j = 0; j < H - i-1 ;j++){
    
                System.out.print("  ");
            }
            System.out.print("* ");
            for (int j = 0; j < 2 * i -1; j++) {
    
                System.out.print("  ");
            }
            if (i == 0) {
    
                System.out.print("");
            } else {
    
                System.out.print("*");
            }
            System.out.println();
        }
        for (int i = 0; i < 2 * H - 1; i++) {
    
            System.out.print("* ");
        }
    }

9. 一个循环，打印输出一个由字符构成的正方形图案，其中 边长由用户输入确定。要求字符按照以下顺序循环使 用：‘#’ , ‘@’, ‘*’。例如，当边长为 5 时，输出如下：

public static void main(String[] args) {
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入边长");
        int sideLength = scanner.nextInt();

        System.out.print("# ");//左上角 #
        for (int j = 0; j < sideLength - 2; j++) {
    //上边 @ @ @
            System.out.print("@ ");
        }
        System.out.print("# ");// 右上角 #


        System.out.println();//换行


        for (int i = 0; i < sideLength - 2; i++) {
    //中间内容
            System.out.print("@ ");
            for (int j = 0; j < sideLength - 2; j++) {
    
                System.out.print("* ");
            }
            System.out.print("@ ");
            System.out.println();
        }


        System.out.print("# ");
        for (int j = 0; j < sideLength - 2; j++) {
    
            System.out.print("@ ");
        }
        System.out.print("# ");
        System.out.println();
    }