java排序之冒泡排序

代码：

package com.cn.algorithm_arithmetic算法;
/**
 * 本程序记录了经典排序算法之冒泡排序
 * @author Administrator
 *
 */

public class Bubble_Sort {
        //冒泡排序优化前
        public static void bubble_sort(int [] a){
        for (int i = 0; i < a.length-1; i++) {
            for (int j = 0; j < a.length-i-1; j++) {
                if (a[j+1] < a[j]){
                    int temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                }
            }
        }
        }
        
        //冒泡排序优化后
        public static int[] bubble_sort_optimize(int a[]){
            for (int i = 0; i < a.length-1; i++) {
                boolean exchange = false;
                for (int j = 0; j < a.length-i-1; j++) {
                    if (a[j+1]<a[j]){
                        int tmp = a[j];
                        a[j] = a[j+1];
                        a[j+1]=tmp;
                        exchange = true;
                    }
                
                }
                if (exchange = false){
                    break;
                }
            }
            return a;
        }

    public static void main(String[] args) {
        System.out.println("--------------优化前--------------");
        System.out.print("冒泡排序优化前原始数据:");
        int a[] = new int[5];
        for (int i = 0; i < a.length; i++) {
            a[i] = (int)(Math.random()*100);
            System.out.print(a[i]+"  ");
        }
        bubble_sort(a);
        System.out.print("
冒泡排序优化前新数据:");
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i]+"  ");
        }
        System.out.println("
---------------优化后--------------");
        //冒泡排序
        System.out.print("冒泡排序优化后原始数据:");
        int a1[] = new int[5];
        for (int i = 0; i < a1.length; i++) {
            a1[i] = (int)(Math.random()*100);
            System.out.print(a1[i]+"  ");
        }
        bubble_sort_optimize(a1);
        System.out.print("
冒泡排序优化后新数据:");
        for (int i = 0; i < a1.length; i++) {
            System.out.print(a1[i]+"  ");
        }
    }

}

冒泡排序的时间复杂度：理想O(n),平均O(n^2),助记口决：外管轮询内管排