java集合排序——Collections.sort()的两种用法

转自：http://gwh-08.iteye.com/blog/1233401

 /**
 * @author guwh
 * @version 创建时间：2011-11-3 上午10:49:36
 * 类说明
 */
 package com.jabberchina.test;

 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;

 public class SortTest {



     public static void main(String[] args) {
         List<String> lists = new ArrayList<String>();
         List<A> list = new ArrayList<A>();
         List<B> listB = new ArrayList<B>();
         lists.add("5");
         lists.add("2");
         lists.add("9");
         //lists中的对象String 本身含有compareTo方法，所以可以直接调用sort方法，按自然顺序排序，即升序排序
         Collections.sort(lists);

         A aa = new A();
         aa.setName("aa");
         aa.setOrder(1);
         A bb = new A();
         bb.setName("bb");
         bb.setOrder(2);
         list.add(bb);
         list.add(aa);
         //list中的对象A实现Comparable接口
         Collections.sort(list);

         B ab = new B();
         ab.setName("ab");
         ab.setOrder("1");
         B ba = new B();
         ba.setName("ba");
         ba.setOrder("2");
         listB.add(ba);
         listB.add(ab);
         //根据Collections.sort重载方法来实现
         Collections.sort(listB,new Comparator<B>(){
             @Override
             public int compare(B b1, B b2) {
                 return b1.getOrder().compareTo(b2.getOrder());
             }

         });

         System.out.println(lists);
         System.out.println(list);
         System.out.println(listB);

     }

 }

 class A implements Comparable<A>{
     private String name;
     private Integer order;
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }

     public Integer getOrder() {
         return order;
     }
     public void setOrder(Integer order) {
         this.order = order;
     }
     @Override
     public String toString() {
         return "name is "+name+" order is "+order;
     }
     @Override
     public int compareTo(A a) {
         return this.order.compareTo(a.getOrder());
     }

 }

 class B{
     private String name;
     private String order;
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public String getOrder() {
         return order;
     }
     public void setOrder(String order) {
         this.order = order;
     }
     @Override
     public String toString() {
         return "name is "+name+" order is "+order;
     }
 }

 打印的结果为：
  [2, 5, 9]
 [name is aa order is 1, name is bb order is 2]
 [name is ab order is 1, name is ba order is 2]