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] } }