熟能生巧！

冒泡、选择、插入

public class OrdinarySortRepeat {
    public static void main(String[] args) {
        int[] arr = getRandomInts(10);
        int[] arr2 = Arrays.copyOf(arr,10);
        int[] arr3 = Arrays.copyOf(arr,10);
        int[] arr4 = Arrays.copyOf(arr,10);
        System.out.println("origin:"+Arrays.toString(arr));
        bubbleSort(arr);
        System.out.println("bubbleSort:"+Arrays.toString(arr));
        selectSort(arr2);
        System.out.println("selectSort:"+Arrays.toString(arr2));
        insertSort(arr3);
        System.out.println("insertSort:"+Arrays.toString(arr3));
        insertSort2(arr4);
        System.out.println("insertSort2:"+Arrays.toString(arr4));
    }
    public static int[] getRandomInts(int length){
        int[] numbers = new int[length];
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            numbers[i] = random.nextInt(9999);
        }
        return numbers;
    }

    public static void swap(int[] arr, int a, int b){
        int temp = arr[a];
        arr[a] = arr[b];
        arr[b] = temp;
    }

    public static void bubbleSort(int[] arr){
        for(int i = 0; i < arr.length-1; i++){
            boolean isNoSorted = true;
            for(int j = 0; j < arr.length-i-1; j++){
                if(arr[j] > arr[j+1]){
                    swap(arr,j,j+1);
                    isNoSorted = false;
                }
            }
            if(isNoSorted){
                return;
            }
        }
    }

    public static void selectSort(int[] arr){
        for(int i = 0; i < arr.length-1; i++){
            for(int j = i+1; j < arr.length;j++){
                if(arr[i] > arr[j]){
                    swap(arr,i,j);
                }
            }
        }
    }

    public static void insertSort(int[] arr){
        for(int i = 1; i < arr.length; i++){
            int temp = arr[i];
            int j = i-1;
            while(j >= 0 && arr[j] > temp){
                arr[j+1] = arr[j];
                j--;
            }
            arr[j+1] = temp;
        }
    }

    public static void insertSort2(int[] arr){
        for(int i = 1;i < arr.length; i++){
            int temp = arr[i];
            int j;
            for(j = i-1; j >= 0; j--){
                if(arr[j] > temp){
                    arr[j+1] = arr[j];
                }else{
                    break;
                }
            }
            arr[j+1] = temp;
        }
    }
}

快速排序

public class QuickSortRepeat {
    public static void main(String[] args) {
        int[] arr = getRandomInts(10);
        int[] arr2 = Arrays.copyOf(arr,10);
        int[] arr3 = Arrays.copyOf(arr,10);
        int[] arr4 = Arrays.copyOf(arr,10);
        System.out.println("origin:"+Arrays.toString(arr));
        quickSort(arr,0,arr.length-1);
        System.out.println("quickSort:"+Arrays.toString(arr));
        quickSort2(arr2,0,arr.length-1);
        System.out.println("quickSort2:"+ Arrays.toString(arr2));
        quickSort3(arr3,0,arr.length-1);
        System.out.println("quickSort3:"+Arrays.toString(arr3));
        quickSort4(arr4,0,arr.length-1);
        System.out.println("quickSort4:"+Arrays.toString(arr4));
    }
    public static int[] getRandomInts(int length){
        int[] numbers = new int[length];
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            numbers[i] = random.nextInt(9999);
        }
        return numbers;
    }

    public static void swap(int[] arr, int a, int b){
        int temp = arr[a];
        arr[a] = arr[b];
        arr[b] = temp;
    }

    /**
     * 根据阮一峰博客：http://www.ruanyifeng.com/blog/2011/04/quicksort_in_javascript.html
     * @param arr
     * @param left
     * @param right
     */
    public static void quickSort(int[] arr, int left, int right){
        if(left >= right){
            return;
        }
        int standard = arr[left];
        int index = left;
        for(int i = left+1; i <= right; i++){
            if(arr[i] < standard){
                arr[index] = arr[i];
                for(int j = i-1; j > index;j--){
                    arr[j+1] = arr[j];
                }
                arr[++index] = standard;
            }
        }
        quickSort(arr,left,index-1);
        quickSort(arr,index+1,right);
    }

    /**
     * 根据马桶上看算法：http://developer.51cto.com/art/201403/430986.htm
     * @param arr
     * @param left
     * @param right
     */
    public static void quickSort2(int[] arr,int left, int right){
        if(left >= right){
            return;
        }
        int standard = arr[left];
        int i = left;
        int j = right;
        while(i < j){
            while(i < j && arr[j] >= standard){
                j--;
            }
            while(i < j && arr[i] <= standard){
                i++;
            }
            if(i < j){
                swap(arr,i,j);
            }else{
                break;
            }
        }
        if(i != left){
            arr[left] = arr[i];
            arr[i] = standard;
        }

        quickSort2(arr,left,i-1);
        quickSort2(arr,i+1,right);
    }

    /**
     * 根据博客园：https://www.cnblogs.com/coderising/p/5708801.html
     * @param arr
     * @param left
     * @param right
     */
    public static void quickSort3(int[] arr, int left, int right){
        if(left >= right){
            return;
        }
        int standard = arr[left];
        int i = left;
        int j = right;
        while(i < j){
            while(i < j && arr[j] >= standard){
                j--;
            }
            arr[i] = arr[j];
            while(i < j && arr[i] <= standard){
                i++;
            }
            arr[j] = arr[i];
        }
        arr[i] = standard;
        quickSort3(arr,left,i-1);
        quickSort3(arr,i+1,right);
    }

    /**
     * 同上，对quickSort3进行优化(三数取中)，也是根据博客园：https://www.cnblogs.com/coderising/p/5708801.html
     * @param arr
     * @param left
     * @param right
     */
    public static void quickSort4(int[] arr, int left, int right){
        if(left >= right){
            return;
        }
        int mid = (left+right)/2;
        if(arr[right] < arr[left]){
            swap(arr,left,right);
        }
        if(arr[right] < arr[mid]){
            swap(arr,mid,right);
        }
        if(arr[left] < arr[mid]){
            swap(arr,left,mid);
        }
        int standard = arr[left];
        int i = left;
        int j = right;
        while(i < j){
            while(i < j && arr[j] >= standard){
                j--;
            }
            arr[i] = arr[j];
            while(i < j && arr[i] <= standard){
                i++;
            }
            arr[j] = arr[i];
        }
        arr[i] = standard;
        quickSort3(arr,left,i-1);
        quickSort3(arr,i+1,right);
    }
}