Java SE---Collection

package com.an.collection;

import java.util.*;
import java.util.Map;

/**
 * @description:
 * @author: anpeiyong
 * @date: Created in 2020/3/4 9:30
 * @since:
 */
public class MapTest {

    public static void main(String[] args) {
//        iteratorTest();
//        iteratorTest2();
//        foreachTest();
//        foreachTest2();
//        foreachMethodTest();
        valuesTest();
    }

    public static void iteratorTest(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        Set<String> keySet=map.keySet();
        Iterator<String> iterator =keySet.iterator();
        while (iterator.hasNext()){
            String key=iterator.next();
            System.out.println(map.get(key));
        }
    }

    public static void iteratorTest2(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        Set<Map.Entry<String,String>> entrySet=map.entrySet();
        Iterator<Map.Entry<String,String>> entryIterator=entrySet.iterator();
        while (entryIterator.hasNext()){
            Map.Entry<String,String> entry=entryIterator.next();
            String key=entry.getKey();
            String value=entry.getValue();

            System.out.println(key+":"+value+"==");
        }
    }

    public static void foreachTest(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");
        
        Set<String> keySet=map.keySet();
        for (String s:keySet) {
            System.out.println(map.get(s));
        }
    }

    public static void foreachTest2(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        Set<Map.Entry<String,String>> entrySet=map.entrySet();
        for (Map.Entry<String,String> s:entrySet) {
            System.out.println(s.getKey()+":"+s.getValue());
        }
    }

    public static void foreachMethodTest(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        map.forEach((k,v)->{
            System.out.println(k+":"+v);
        });
    }

    public static void valuesTest(){
        HashMap<String,String> map=new HashMap<>();
        map.put("1","a");
        map.put("2","b");
        map.put("3","c");

        Collection<String> collection =map.values();
        System.out.println(collection);
    }

}