CopyOnWriteArrayList In Java

CopyOnWriteArrayList:

public class CopyOnWriteArrayList<E>
extends Object
implements List<E>, RandomAccess, Cloneable, Serializable

All Implemented Interfaces:
Serializable, Cloneable, Iterable<E>, Collection<E>, List<E>, RandomAccess

• CopyOnWriteArrayList belong to java.util.concurrent package.
• CopyOnWriteArrayList class is introduced in JDK 1.5
• CopyOnWriteArrayList Implements the List interface.
• CopyOnWriteArrayList is a thread-safe variant of ArrayList.
• null can be added to the list.
• Iterator of CopyOnWriteArrayList will never throw ConcurrentModificationException. That means fail-safe 
• CopyOnWriteArrayList creates a Cloned copy of underlying ArrayList, for every update operation and synchronized automatically.
• Iterator of CopyOnWriteArrayList we can not perform remove, set and add operation otherwise it will throw UnsupportedOperationException at Run-time exception. Iterator of CopyOnWriteArrayList will never throw ConcurrentModificationException.

CopyOnWriteArrayList Example:

package com.javaiq.in;

import java.util.Iterator;
import java.util.concurrent.CopyOnWriteArrayList;

public class CopyOnWriteArrayListExample {

	public static void main(String args[]) {
		// create an array list
		CopyOnWriteArrayList cowList = new CopyOnWriteArrayList();
		System.out.println("Initial size of CopyOnWriteArrayList: " + cowList.size());

		// add elements to the CopyOnWriteArrayList
		cowList.add("Amit");
		cowList.add("Sumit");
		cowList.add("Sonu");
		cowList.add("Raj");
		cowList.add("Kapil");
		cowList.add("PK");
		cowList.add(1, "JK");
		System.out.println("Size of CopyOnWriteArrayList after add elements: " + cowList.size());

		// display list elements
		System.out.println("Contents of CopyOnWriteArrayList: " + cowList);

		// Remove elements from the CopyOnWriteArrayList
		cowList.remove("Amit");
		cowList.remove(3);
		System.out.println("Size of al after deletions: " + cowList.size());
		System.out.println("Contents of CopyOnWriteArrayList: " + cowList);

		try {
			Iterator iterator = cowList.iterator();
			while (iterator.hasNext()) {
				iterator.remove();
			}
		} catch (UnsupportedOperationException e) {
			System.out.println("Remove Method does not supported:");
		}

		System.out.println("Size of CopyOnWriteArrayList: " + cowList.size());
	}
}

Output:

Initial size of CopyOnWriteArrayList: 0
Size of CopyOnWriteArrayList after add elements: 7
Contents of CopyOnWriteArrayList: [Amit, JK, Sumit, Sonu, Raj, Kapil, PK]
Size of al after deletions: 5
Contents of CopyOnWriteArrayList: [JK, Sumit, Sonu, Kapil, PK]
Remove Method does not supported:
Size of CopyOnWriteArrayList: 5

How does CopyOnWriteArrayList work internally in Java?

How does CopyOnWriteArrayList work in Java?

Is CopyOnWriteArrayList synchronized?

Yes, CopyOnWriteArrayList is to be used in a Multi Thread(concurrent environment.) based environment. this is useful where read operations are very frequent and update operations are rare.

What is difference between ArrayList and CopyOnWriteArrayList?

Related Tutorials 

• Java Collections Interview
• List Interface In Java
• ArrayList
• LinkedList
• Custom Own ArrayList Implementation
• Custom LinkedList implementation in java
• Set Interface In Java
• Map Interface In Java
• HashMap
• TreeMap
• HashMap Vs ConcurrentHashMap
• HashMap Vs HashTable In Java
• HashMap Vs HashSet In Java
• HashMap Vs TreeMap In Java
• HashMap vs LinkedHashMap In Java
• TreeSet Vs TreeMap In Java
• SortedSet Vs TreeSet In Java
• SortedMap Vs TreeMap In Java
• Array Vs ArrayList In Java
• ArrayList Vs LinkedList In Java
• How HashSet Works Internally
• How TreeMap Works Internally
• How HashMap Works Internally
• How ConcurrentHashMap Works Internally
• How To Detect Loop In A LinkedList In Java
• Detect And Remove Loop In A LinkedList