Java Collections synchronizedList() Method

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

Syntax

Following is the declaration of synchronizedList() method:

Parameter

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

Returns

The synchronizedList() method returns a synchronized view of the specified List.

Exceptions

Compatibility Version

Java 1.5 and above

Example 1

import java.util.*;
public class CollectionsSynchronizedListExample1 {
	public static void main(String[] args) {		       
		//Create ArrayList object 
	      List<String> list = new ArrayList<String>();
	      //Add values in the list
	      list.add("A");
	      list.add("B");
	      list.add("C");
	      list.add("D");
	      list.add("E");
	      //Create a synchronized list
	      List<String> synlist = Collections.synchronizedList(list);
	      System.out.println("Synchronized list is :"+synlist);
	      }
}

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Output:

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

Example 2

import java.util.*;
public class CollectionsSynchronizedListExample2 {
	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 List
	      List<Integer> coll = Collections.synchronizedList(list);
	      System.out.println("Synchronized list is :"+coll);
	      }
}

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Output:

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

Example 3

import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class CollectionsSynchronizedListExample3 {
	public static void main(String[] args) throws InterruptedException {	       
		List<Integer> integers = new ArrayList<>();
            List<Integer> list = Collections.synchronizedList(integers);
            Collections.addAll(list, new Integer[10000]);
            System.out.println("Initial size: " + list.size());
            final ExecutorService e = Executors.newFixedThreadPool(10);
            for (int i = 0; i < list.size(); i++) {
                e.execute(() -> list.remove(0));
            }
            e.shutdown();
            e.awaitTermination(1000, TimeUnit.SECONDS);
            System.out.println(list.size());//should be zero
	      }
}

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Output: