Difference Between Concurrent Hashmap Vs Synchronized Hashmap

Synchronized HashMap

A synchronized HashMap is a regular HashMap wrapped with synchronization mechanisms to make it thread-safe. This is typically achieved by using external synchronization, such as the synchronized keyword or using locks. Every method that modifies the map (e.g., put, remove, etc.) is synchronized, ensuring that only one thread can modify the map at a time.

Need for Concurrent and Synchronized Hashmap

Even though we have a hashmap, why do we still need a concurrent and synchronized hashmap? 

Normal hashmap is ineffective when working in a concurrent multithreaded environment, and thread safety is a priority. Concurrency means running more than one program or application in parallel with the help of threads. Threads are a light weighted processes in a process. 

The alternative to this problem was a concurrent and synchronized hashmap. We can work in a concurrent multithreading environment with the help of concurrent hashmap and synchronized hashmap.

Now let's talk about concurrent hashmap vs synchronized hashmap, which is our main focus for this blog. We will discuss some points to clarify the concurrent hashmap vs synchronized hashmap. Also, we implement both of the classes in a java program to have a proper understanding of concurrent hashmap vs synchronized hashmap.

Concurrent Hashmap vs Synchronized Hashmap

The above points cover the concurrent hashmap vs synchronized hashmap. Now let's discuss the implementation of concurrent and synchronized hashmap so you can better understand the topic of concurrent hashmap vs synchronized hashmap.

Implementation

• Java

Java

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class Main
{
public static void main(String[] args) {

    /* Initializing a synchronized Hashmap interface*/
  Map<Integer,String> syncMap = Collections.synchronizedMap(new HashMap<Integer, String>());
                /*Try catch block demonstrate the synchronized hashmap */
  try {
      syncMap.put(null,null);
  } catch(Exception e) {
      System.out.println("error in syncMap");
  }
   
  /* Initializing a concurrent Hashmap interface*/
  ConcurrentHashMap<Integer, String> concMap = new ConcurrentHashMap<>();
  try {
      concMap.put(null,null);
  } catch(Exception e) {
      System.out.println("null key-value pair is invalid in ConcurrentHashMap");
  }
}
}

You can also try this code with Online Java Compiler

Run Code

The above programs show how we can implement both concurrent and synchronized hashmaps. As mentioned in the blog, to implement a synchronized hashmap, you need to import the collection class in java and the concurrent class to implement a concurrent hashmap.

This program shows that we can use null key-value pair in a synchronized hashmap but not in a concurrent hashmap which is one of the differences in concurrent hashmap vs synchronized hashmap.

With all the mentioned points and content, we hope you have understood the concurrent hashmap vs synchronized hashmap means the difference between them.

You can also read about the Longest Consecutive Sequence.

Frequently Asked Questions

Why ConcurrentHashMap is faster than HashMap?

ConcurrentHashMap is faster than HashMap due to its segmented structure, allowing concurrent access by multiple threads without contention.

Is synchronized and concurrent hashmap both thread-safe?

 Synchronized hashmap and concurrent hashmap are both thread-safe.

Which one is better in terms of performance concurrent hashmap or synchronized hashmap?

Concurrent hashmap is better than synchronized because it provides high concurrency in multithreading.

Which one is better in a single threading environment concurrent hashmap or synchronized hashmap?

For a single threading environment, a synchronized hashmap is more suitable.

Can we use null key-value pair in a synchronized hashmap?

Yes, we can use null key-value pair in a synchronized hashmap.

Conclusion

This blog discussed the difference between a concurrent hashmap and a synchronized hashmap. We have mentioned many points to clarify their differences and implemented a java program to showcase the differences more clearly.

Check out this problem - Pair Sum In Array.

To learn more about java, check out the following articles.

• entryset java
• Hash Function in Data Structure
• Internal Working of HashMap
• HashMap entrySet() Method in Java
• IdentityHashMap in Java
• flatMap() Method in Java
• ConcurrentHashMap in Java
• Difference Between IOT and M2M

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