6,求最大公约数和最小公倍数

import java.util.Scanner;

public class HCFandLCM {
    public static void main(String[] args) {
        int a, b, m;
        Scanner scanner = new Scanner(System.in);
        System.out.print("Please input a int number: ");
        a = scanner.nextInt();
        System.out.print("Please input a int number again: ");
        b = scanner.nextInt();
        HCF hcf = new HCF();
        m = hcf.DE(a, b);
        int n = a * b / m;
        System.out.println("HCF IS:" + m);
        System.out.println("LCM IS:" + n);

    }
}
//求最大公约数
class HCF {
    public int DE(int x, int y) {
        int t;
        if (x < y) {
            t = x;
            x = y;
            y = t;
        }
        while (y != 0) {
            if (x == y)
                return x;
            else {
                int k = x % y;
                x = y;
                y = k;
            }
        }
        return x;
    }
}

7，求不同字符的个数：

import java.util.Scanner;

public class CountEnglishcharSpaceNumberOther {
    public static void main(String[] args) {
        int abcCount = 0;
        int spaceCount = 0;
        int numCount = 0;
        int otherCount = 0;
        Scanner scanner = new Scanner(System.in);
        String string = scanner.nextLine();
        // Converts this string to a new character array.
        char[] ch = string.toCharArray();
        for (int i = 0; i < ch.length; i++) {
            if (Character.isLetter(ch[i])) {
                abcCount++;
            } else if (Character.isDigit(ch[i])) {
                numCount++;
            } else if (Character.isSpaceChar(ch[i])) {
                spaceCount++;
            } else {
                otherCount++;
            }
        }
        System.out.println("THe number of abc: " + abcCount);
        System.out.println("The number of nubmer: " + numCount);
        System.out.println("The number of space: " + spaceCount);
        System.out.println("Ther number of others: " + otherCount);
    }
}

8，n个a+aa+……aaaa相加

import java.util.Scanner;

public class aaa {
    public static void main(String[] args) {
        long a, b = 0, sum = 0;
        Scanner scanner = new Scanner(System.in);
        System.out.print("Please input the value of a: ");
        a = scanner.nextInt();
        System.out.print("Please input the value of n: ");
        int n = scanner.nextInt();
        int i = 0;
        while (i < n) {
            b = b + a;
            sum = sum + b;
            a = a * 10;
            ++i;
        }
        System.out.println(sum);
    }
}

9,求1000内的完数：

public class PerfectNum {
    public static void main(String[] args) {
        System.out.println("The perfect number between 1 and 1000 is :");
        for (int i = 1; i < 1000; i++) {
            int t = 0;
            for (int j = 1; j <= i / 2; j++) {
                if (i % j == 0) {
                    t = t + j;
                }
            }
            if (t == i) {
                System.out.println(i + " ");
            }
        }
    }
}

10，落球第十次的路程和高度：

public class Ball {
    public static void main(String[] args) {
        double h = 100, s = 100;
        for (int i = 1; i < 10; i++) {
            s = s + h;
            h = h / 2;
        }
        System.out.println("The path :" + s);
        System.out.println("The High :" + h / 2);
    }
}

问题6-10