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<i; j++)

                System.out.print("*");

            System.out.println(
9fee
);

        }

    }

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 + "    ");

            }

        }