冒牌排序、快速排序、九九乘法表、菱形、三角形、倒立三角形、回数、素数

冒泡排序：

 public static void main(String[] args) {
        int arr[] ={12,20,30,45,99,66,33,22,66,22,100};
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr.length - 1; j++) {
                if(arr[j] < arr[j+1]){
                    int l = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = l;
                }
            }
        }
        for (int i : arr) {
            System.out.print(i+" ");
        }
    }

快速排序：

public class QuickSort {
    /**
     * 快速排序
     *
     * @param strDate
     * @param left
     * @param right
     */
    public void quickSort(String[] strDate, int left, int right) {
        String middle, tempDate;
        int i, j;
        i = left;
        j = right;
        middle = strDate[(i + j) / 2];
        do {
            while (strDate[i].compareTo(middle) < 0 && i < right)
                i++; // 找出左边比中间值大的数
            while (strDate[j].compareTo(middle) > 0 && j > left)
                j--; // 找出右边比中间值小的数
            if (i <= j) { // 将左边大的数和右边小的数进行替换
                tempDate = strDate[i];
                strDate[i] = strDate[j];
                strDate[j] = tempDate;
                i++;
                j--;
            }
        } while (i <= j); // 当两者交错时停止

        if (i < right) {
            quickSort(strDate, i, right);// 从
        }
        if (j > left) {
            quickSort(strDate, left, j);
        }
    }

    /**
     *   * @param args  
     */
    public static void main(String[] args) {
        String[] strVoid = new String[] { "11", "66", "22", "0", "55", "22", "0", "32" };
        QuickSort sort = new QuickSort();
        sort.quickSort(strVoid, 0, strVoid.length - 1);
        for (int i = 0; i < strVoid.length; i++) {
            System.out.println(strVoid[i] + " ");
        }
    }

}

九九乘法表：
    public static void main(String[] args) {
        for (int i = 1; i <= 9; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(j+"*"+i+"="+i*j+"  ");
            }
            System.out.println("  ");
        }
    }

菱形：

 public static void main(String[] args) {
        int arr[] ={12,20,30,45,99,66,33,22,66,22,100};
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr.length - 1; j++) {
                if(arr[j] < arr[j+1]){
                    int l = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = l;
                }
            }
        }
        for (int i : arr) {
            System.out.print(i+" ");
        }
    }

三角形：

public static void main(String[] args){
        for(int i=1;i<=5;i++){
            for(int j=5; i<=j; j--)
                System.out.print(" ");
            for(int j=1; j<=i; j++)
                System.out.print("*");
            for(int j=1; j                 System.out.print("*");
            System.out.println();
        }
    }

倒立三角形：

public static void main(String[] args) {
        //打印倒立的三角形
       for (int m = 1; m <= 4; m++) {
           //打印空格
           for (int n = 0; n <= m; n++) {
               System.out.print(" ");
           }
           //打印*
           for (int x = 1; x <= 7 -2 * (m - 1); x++) {
               System.out.print("*");
           }
           System.out.println();
       }        
   }

回数：

 public static void main(String[] args) {  
          
            Scanner sc = new Scanner(System.in);  
            System.out.println("请输入一个整数：");  
            int num = sc.nextInt();  
      
            String str1 = num + "";  
      
            StringBuilder str2 = new StringBuilder(str1);  
            str2.reverse();  
            int count = 0;  
      
            for (int i = 0; i < str1.length(); i++) {  
                if (str1.charAt(i) != str2.charAt(i)) {  
                    System.out.println(str1 + "不是回文数");  
                    break;  
                } else {  
                    count++;  
                }  
            }  
            if (count == str1.length()) {  
                System.out.println(str1 + "是回文数");  
            }  
        } 

素数（质数）（3-100以内的质数）：

     int j;
        boolean flag;
        for (int i = 3; i < 100; i++) {
            flag = false;
            for (j = 2; j <= Math.sqrt(i); j++) {
                if (i % j == 0) {
                    flag = true;
                    break;
                }
            }
            if (flag == false) {
                System.out.print(i + "    ");
            }
        }