Java Long class

Java Collections synchronizedMap() Method

Last Updated : 17 Mar 2025

The synchronizedMap() method of Java Collections class is used to get a synchronized (thread-safe) map backed by the specified map.

Syntax

Following is the declaration of synchronizedMap() method:

Parameter

Parameter	Description	Required/Optional
m	It is the map which will be wrapped in a synchronized map.	Required

Returns

The synchronizedMap() method returns a synchronized view of the specified Map.

Exceptions

Example 1

import java.util.*;
public class CollectionsSynchronizedMapExample1 {
	public static void main(String[] args) {
		Map<String, String> map = new HashMap<String, String>();
		map.put("1", "Rahul");
		map.put("4", "Karan");
		map.put("3", "Mohan");
		Map<String, String> synmap = Collections.synchronizedMap(map);
		System.out.println("Synchronized map is :" + synmap);	            
	      }
}

Output:

Synchronized map is :{1=Rahul, 3=Mohan, 4=Karan}

Example 2

import java.util.*;
public class CollectionsSynchronizedMapExample2 {
	public static void main(String[] args) {
		Map<Integer, Integer> map = new HashMap<>();
		map.put(1, 1001);
		map.put(2, 1002);
		map.put(3, 1003);
		map.put(4, 1004);
		map.put(5, 1005);
		System.out.println("Map before Synchronized map: " + map);		
		Map<Integer, Integer> synmap = Collections.synchronizedMap(map);	
	      map.remove(4, 1004);
	     System.out.println("Synchronized map after remove(4, 1004):" + synmap);
	     }
}

Output:

Map before Synchronized map: {1=1001, 2=1002, 3=1003, 4=1004, 5=1005}
Synchronized map after remove(4, 1004):{1=1001, 2=1002, 3=1003, 5=1005}

Example 3

import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
public class CollectionsSynchronizedMapExample3 {
	private static AtomicInteger counter = new AtomicInteger();
	public static void main(String[] args) throws  InterruptedException{
	     Map<Integer, Integer> m = new HashMap<>();
	     Map<Integer, Integer> map = Collections.synchronizedMap(m);
	     final ExecutorService e = Executors.newFixedThreadPool(10);
	     for (int i = 0; i < 10000; i++) {
	            e.execute(() -> map.put(counter.incrementAndGet(),
	            (int) (Math.random() * 100)));
	            }
	     e.shutdown();
	     e.awaitTermination(1000, TimeUnit.SECONDS);
	     System.out.println(map.size());//should be 10000		
	     }
}

Output:

Next TopicJava Collections Class

← prev next →

We deliver comprehensive tutorials, interview question-answers, MCQs, study materials on leading programming languages and web technologies like Data Science, MEAN/MERN full stack development, Python, Java, C++, C, HTML, React, Angular, PHP and much more to support your learning and career growth.

Contact info

G-13, 2nd Floor, Sec-3, Noida, UP, 201301, India

hr@tpointtech.com

+91-9599086977

Interview Questions

Python Java Data Structure C++ C HTML JavaScript jQuery SQL Power BI

Online Compilers

C Compiler R Compiler C++ Compiler PHP Compiler Java Compiler HTML Editor Swift Compiler Python Compiler JavaScript Editor TypeScript Editor

Latest Post | Tutorials List | Privacy Policy | About Us | Contact Us

Java Collections synchronizedMap() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

Contact info

Follow us

Top Tutorials

Interview Questions

Online Compilers

Java String Methods

Java Array Class

Java Math Methods

ArrayList Methods

Java List Methods

Java Thread Methods

Java Date Class

Java Collection Methods

Java ListIterator Class

Java NIO Tutorial

HttpURLConnection

Java Deque

Java HttpCookie Class

Java URL class

Java Vector class

Java Socket Class

Java Executors

Java Integer Class

Java IdentityHashMap

Java ArrayBlockingQueue

Java Timestamp

Java Spliterator

Java Bitset

Java Instant

Java Compiler Class

Java AtomicInteger Class

Java AtomicLong Methods

Java Authenticator

Java BigDecimal class

Big Integer Class

Java Boolean class

Java Byte Class

Java Class

Java Collections class

CopyOnWriteArrayList

LinkedBlockingDeque

Java Long class

LinkedTransferQueue

Java List

Java MulticastSocket

Java Number Class

Java Phaser Class

Java Collections synchronizedMap() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

Related Posts

Subscribe to Tpoint Tech

Contact info

Follow us

Top Tutorials

Interview Questions

Online Compilers