Java ConcurrentHashMap和SynchronizedHashMap的区别

ConcurrentHashMap和SynchronizedHashMap都是线程安全的集合类，可以在多线程和并发的java应用程序中使用。但是它们之间存在着一些差异。在这篇文章中，我们试图涵盖它们之间的所有这些差异。

1. 因此，在同一时间，16个更新操作可以由线程执行。

ConcurrentHashMap演示。

// Java Program to demonstrate the
// working of ConcurrentHashMap
 
import java.util.*;
import java.util.concurrent.*;
 
public class TraversingConcurrentHashMap {
 
    public static void main(String[] args)
    {
 
        // create an instance of ConcurrentHashMap
        ConcurrentHashMap<Integer, String> chmap
            = new ConcurrentHashMap<Integer, String>();
 
        // Add elements using put()
        chmap.put(10, "Geeks");
        chmap.put(20, "for");
        chmap.put(30, "Geeks");
        chmap.put(40, "Welcome");
        chmap.put(50, "you");
 
        // Create an Iterator over the
        // ConcurrentHashMap
        Iterator<ConcurrentHashMap.Entry<Integer, String> >
            itr = chmap.entrySet().iterator();
 
        // The hasNext() method is used to check if there is
        // a next element and the next() method is used to
        // retrieve the next element
        while (itr.hasNext()) {
            ConcurrentHashMap.Entry<Integer, String> entry
                = itr.next();
            System.out.println("Key = " + entry.getKey()
                               + ", Value = "
                               + entry.getValue());
        }
    }
}

输出

Key = 50, Value = you
Key = 20, Value = for
Key = 40, Value = Welcome
Key = 10, Value = Geeks
Key = 30, Value = Geeks

2.Synchronized HashMap： Java HashMap是一个非同步化的集合类。如果我们需要对它进行线程安全的操作，那么我们必须明确地对它进行同步。java.util.Collections类的synchronizedMap()方法被用来同步化它。它返回一个由指定Map支持的同步（线程安全）Map。

同步的HashMap演示。

// Java program to demonstrate the
// working of Synchronized HashMap
 
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
 
public class SynchronizedHashMap {
    public static void main(String args[])
    {
 
        // Creating a HashMap
        HashMap<Integer, String> hmap
            = new HashMap<Integer, String>();
 
        // Adding the elements using put method
        hmap.put(10, "Geeks");
        hmap.put(20, "for");
        hmap.put(30, "Geeks");
        hmap.put(25, "Welcome");
        hmap.put(40, "you");
 
        // Creating a synchronized map
        Map map = Collections.synchronizedMap(hmap);
        Set set = map.entrySet();
 
        // Synchronize on HashMap, not on set
        synchronized (map)
        {
            Iterator i = set.iterator();
            // Printing the elements
            while (i.hasNext()) {
                Map.Entry me = (Map.Entry)i.next();
                System.out.print(me.getKey() + ": ");
                System.out.println(me.getValue());
            }
        }
    }
}

输出

20: for
40: you
25: Welcome
10: Geeks
30: Geeks

ConcurrentHashMap和Synchronized HashMap的区别。