Java实现冒泡排序

package com.xzc.arrays;

import java.util.Arrays;

public class BubbleSort {
    //Java实现冒泡排序
    public static void main(String[] args) {
        int[] a = {5, 2, 4, 20, 10, 3, 8};
        int temp;
        for(int i = 0;i<a.length-1;++i){
            for(int j = 0;j<a.length-1;++j){
                if(a[j]>a[j+1]){
                    temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                }
            }
        }
        System.out.println(Arrays.toString(a));//[2, 3, 4, 5, 8, 10, 20]
    }
}

思考:若数组传进来时就是有序的上述代码实现仍然会遍历。

所以以下为冒泡排序的优化:

package com.xzc.arrays;

import java.util.Arrays;

public class BubbleSort {
    //Java优化冒泡排序
    public static void main(String[] args) {
        int[] a = {5, 2, 4, 20, 10, 3, 8};
        int temp;
        int flag;
        for(int i = 0;i<a.length-1;++i){
            flag = 0;
            for(int j = 0;j<a.length-1;++j){
                if(a[j]>a[j+1]){
                    temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                    flag++;
                }
            }
            if(flag==0){
                break;
            }
        }
        System.out.println(Arrays.toString(a));//[2, 3, 4, 5, 8, 10, 20]
    }
}