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("\n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("\n---------------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("\n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