Java Collections synchronizedCollection() Method

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

Syntax

Following is the declaration of synchronizedCollection() method:

Parameter

Parameter	Description	Required/Optional
c	It is the collection to be "wrapped" in a synchronized collection.	Required

Returns

The synchronizedCollection() method returns a synchronized view of the specified collection.

Exceptions

Compatibility Version

Java 1.5 and above

Example 1

import java.util.*;
public class CollectionsSynchronizedCollectionExample1 {
	public static void main(String[] args) {		       
		//Create vector object 
	      Vector<String> vector = new Vector<String>();
	      //Add values in the vector
	      vector.add("A");
	      vector.add("B");
	      vector.add("C");
	      vector.add("D");
	      vector.add("E");
	      //Create a synchronized view
	      Collection<String> coll = Collections.synchronizedCollection(vector);
	      System.out.println("Synchronized view is :"+coll);
	      }
}

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Output:

Synchronized view is :[A, B, C, D, E]

Example 2

import java.util.*;
public class CollectionsSynchronizedCollectionExample2 {
	public static void main(String[] args) {		       
		//Create a list with items
	      List<Integer> list = Arrays.asList(44, 55, 99, 77, 88, 66);
	      //Create a synchronized view
	      Collection<Integer> coll = Collections.synchronizedCollection(list);
	      System.out.println("Synchronized view is :"+coll);
	      }
}

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Output:

Synchronized view is :[44, 55, 99, 77, 88, 66]

Example 3

import java.util.*;
public class CollectionsSynchronizedCollectionExample3 {
	public static void main(String[] args) {		       
		Collection<String> obj = new ArrayList<>();
		  obj.add("JavaTpoint"); // not thread safe
		  Collection<String> synObj = Collections.synchronizedCollection(obj);
		  synObj.add("SSSIT"); // thread safe
		  //Below iteration will result in non-deterministic behavior
		  Iterator<String> ite1 = synObj.iterator();
		  while (ite1.hasNext()) {
			  String s = ite1.next();
			  System.out.println(s);
		  }
		  //Below code is the right way to iterate synchronized collection
		  synchronized(synObj) { 
			  Iterator<String> ite2 = synObj.iterator();
			  while (ite2.hasNext()) {
				  String s = ite2.next();
				  System.out.println(s);
			  }
		  }
	 }
}

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Output: