Java Collections synchronizedSet() Method

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

Syntax

Following is the declaration of synchronizedSet() method:

Parameter

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

Returns

The synchronizedSet() method returns a synchronized view of the specified Set.

Exceptions

Example 1

import java.util.*;
public class CollectionsSynchronizedSetExample1 {
	public static void main(String[] args) {
		//Create set
	      Set<String> set = new HashSet<String>();
	      //Add values in the set
	      set.add("Facebook");
	      set.add("Twitter");
	      set.add("Whatsapp");
	      set.add("Instagram");
	      //Create a synchronized set
	      Set<String> synset = Collections.synchronizedSet(set);
	      System.out.println("Synchronized set is :"+synset);
	    }
}

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Output:

Synchronized set is :[Twitter, Instagram, Facebook, Whatsapp]

Example 2

import java.util.*;
public class CollectionsSynchronizedSetExample2 {
	public static void main(String[] args) {
		Set<Integer> set = Collections.synchronizedSet(new HashSet<>());
		set.add(101);
		set.add(102);
		set.add(103);
		set.add(104);
		set.add(105);
		System.out.println("Set before Synchronized set: " + set);		
		System.out.println("Set after Synchronized set-");
		//Using iterator must be synchronized manually
		synchronized (set) {
		    Iterator<Integer> iterator = set.iterator();		 
		    while (iterator.hasNext()) {
		        Integer num = iterator.next();
		        System.out.println(num);
		    	  }
		    }     
	     }
}

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Output:

Set before Synchronized set: [101, 102, 103, 104, 105]
Set after Synchronized set-
101
102
103
104
105

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 CollectionsSynchronizedSetExample3 {
    private static AtomicInteger atomicInteger = new AtomicInteger();
    public static void main(String[] args) throws InterruptedException {
        Set<Integer> s = new HashSet<>();
        Set<Integer> set = Collections.synchronizedSet(s);
        System.out.println("initial set size: " + set.size());
        final ExecutorService e = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 1000; i++) {
            e.execute(() -> set.add(atomicInteger.incrementAndGet()));
        }
        e.shutdown();
        e.awaitTermination(1000, TimeUnit.SECONDS);
        System.out.println(set.size());//should be 1000
    }
}

Test it Now

Output: