Java.Collection.Set.List.Collection.ArrayList

//Collections.sort()
//Collection - Set - List 都实现为ArrayList类
//Collection 无排序可重复 Set无排序不可重复 List有排序不可重复

import java.util.*;
class TestSort
{
public static void main(String [] args)
{
ArrayList al=new ArrayList();
al.add(new Integer(1));
al.add(new Integer(3));
al.add(new Integer(2));
System.out.println(al.toString()); //结果：[1,3,2]

Collections.sort(al); //Collections类的sort()方法，对List接口对象排序
System.out.println(al.toString()); //结果：[1,2,3]
}
}