Research on Java Map query time

Summarize the time consumption of the three implementation classes of Map, HashMap, LinkedHashMap, and TreeMap. The example uses String as the key, index to the Integer value and reverse to build the Map. It is not difficult to find the following rules:

Types	HashMap	LinkedHashMap	TreeMap
Map<Integer,String>	112ms, ascending number sort	2ms, ascending number sort	1ms, ascending number sort
Map<String,Integer>	2ms, insertion sequence	<1ms, insertion sequence	<1ms, alphabetical order is increasing

TODO: source code analysis

Not much to say, just go to the code:

import java.util.*;

public class MapDeatil {


    public static void testMap1(){
        Map<Integer, String> hashMap=new HashMap<>();
        hashMap.put(1,"Smith");
        hashMap.put(6,"Ant");
        hashMap.put(3,"AHS");
        hashMap.put(8,"JKA");
        hashMap.put(5,"BVmm");
        long preTime=System.currentTimeMillis();
        hashMap.forEach((num,name)->System.out.println(num+","+name));
        long postTime=System.currentTimeMillis();
        System.out.println("hashset时间："+(postTime-preTime));

        Map<Integer, String> linkedHashMap=new LinkedHashMap<>(hashMap);
        preTime=System.currentTimeMillis();
        linkedHashMap.forEach((num,name)->System.out.println(num+","+name));
        postTime=System.currentTimeMillis();
        System.out.println("hashset时间："+(postTime-preTime));

        Map<Integer,String> treeMap=new TreeMap<Integer, String>(hashMap);
        preTime=System.currentTimeMillis();
        treeMap.forEach((num,name)->System.out.println(num+","+name));
        postTime=System.currentTimeMillis();
        System.out.println("hashset时间："+(postTime-preTime));
    }

    public static void testMap2(){
        Map<String,Integer> hashMap=new HashMap<>();
        hashMap.put("Smith",30);
        hashMap.put("Ant",20);
        hashMap.put("AHS",21);
        hashMap.put("JKA",25);
        hashMap.put("BVmm",33);
        long preTime=System.currentTimeMillis();
        hashMap.forEach((num,name)->System.out.println(num+","+name));
        long postTime=System.currentTimeMillis();
        System.out.println("hashset时间："+(postTime-preTime));

        Map<String, Integer> linkedHashMap=new LinkedHashMap<>(hashMap);
        preTime=System.currentTimeMillis();
        linkedHashMap.forEach((num,name)->System.out.println(num+","+name));
        postTime=System.currentTimeMillis();
        System.out.println("linkedhashset时间："+(postTime-preTime));

        Map<String, Integer> treeMap=new TreeMap<>(hashMap);
        preTime=System.currentTimeMillis();
        treeMap.forEach((num,name)->System.out.println(num+","+name));
        postTime=System.currentTimeMillis();
        System.out.println("treeset时间："+(postTime-preTime));
    }

    public static void main(String[] args) {
        testMap1();
        testMap2();//如果以String为key查询Integer，比反过来更快
    }
}

The output is as follows:

1,Smith
3,AHS
5,BVmm
6,Ant
8,JKA
hashset时间：112
1,Smith
3,AHS
5,BVmm
6,Ant
8,JKA
hashset时间：2
1,Smith
3,AHS
5,BVmm
6,Ant
8,JKA
hashset时间：1
JKA,25
Ant,20
Smith,30
BVmm,33
AHS,21
hashset时间：2
JKA,25
Ant,20
Smith,30
BVmm,33
AHS,21
linkedhashset时间：0
AHS,21
Ant,20
BVmm,33
JKA,25
Smith,30
treeset时间：0