Collection接口的常用方法演示

package com;

import java.util.*;

public class testAll {
    
    
    public static void main(String[] args) {
    
    
        //多态创建只能使用父亲的方法(例如：lingkedlist无法使用头尾插入的操作)
        Collection collection=new Vector();
        Collection collection1=new Stack();
        Collection collection2=new ArrayList();
        Collection collection3=new LinkedList();
        //这也是多态创建
        List list=new LinkedList();
        List list1=new ArrayList();
        List list2=new Vector();
        List list3=new Stack();
        //这也是多态创建
        Vector vector=new Stack();


        ArrayList arrayList=new ArrayList();
        LinkedList linkedList=new LinkedList();
        Vector vector1=new Vector();
        Stack stack=new Stack();



        vector.add(2);
//------------------------------------------------------------
        //以下是Collection的常见方法
        collection.add(1);
        collection.add("A");
        collection.add("A");
        //添加vector中所有元素
        collection.addAll(vector);
        //打印所有元素
        System.out.println("All elements:"+collection.toString());
        //返回集合的hashcode
        System.out.println("hashcode: "+collection.hashCode());
        //集合中是否存在1元素
        System.out.println("是否存在1："+collection.contains(1));
        //包含关系 collection({1,"A","A"})是否包含collection1(空集)
        System.out.println(collection.containsAll(collection));
        //包含关系 collection1(空集)是否包含collection({1,"A","A"})
        System.out.println(collection1.containsAll(collection));
        //判空和大小
        System.out.println(collection.isEmpty()+" "+collection.size());
        System.out.println(collection.isEmpty()+" "+collection.size());
        //删除第一个出现的指定元素
        collection.remove("A");
        System.out.println(collection.isEmpty()+" "+collection.size());
        collection.remove("A");
        System.out.println(collection.isEmpty()+" "+collection.size());

        System.out.println(collection.toString());
        collection2.add(1);
        collection2.add(2);
        //删除与collection2的交集，通俗的说就是删掉collection2中含有的元素
        collection.removeAll(collection2);
        System.out.println(collection.toString());
        
        //下面演示转换成固定大小的数组
        Object[] objects=new Object[collection.size()];
        System.out.println("1:");
        for (Object object : objects) {
    
    
            System.out.println(object);
        }
        //第一种：直接接收
        objects=collection.toArray();
        //第二种，直接传数组引用
        collection.toArray(objects);
        System.out.println("2:");
        for (Object object : objects) {
    
    
            System.out.println(object);
        }
        
//------------------------------------------------------------

    }
}