Get Synchronized List from ArrayList in java

In order to get a synchronized list from an ArrayList, we use the synchronizedList(List <T>) method in Java. The Collections.synchronizedList(List <T>) method accepts the ArrayList as an argument and returns a thread safe list.

Declaration −The Collections.synchronizedList(List <T>) method is declared as follows −

public static List <T> synchronizedList(List <T> list)

Let us see a program to get a synchronized List from ArrayList −

Example

import java.util.*;
public class Example {
   public static void main (String[] args) {
      List<String> list = new ArrayList<String>();
      list.add("Hello");
      list.add("Hi");
      list.add("World");
      list = Collections.synchronizedList(list);
      synchronized(list) {
         Iterator itr = list.iterator();
         while (itr.hasNext())
         System.out.print(itr.next()+" ");
      }
   }
}

Output

Hello Hi World

Collections.synchronizedList() method

The synchronizedList() method is used to synchronize the collections in Java.

Syntax

public static List<T> synchronizedList(List<T> list)

Example

import java.util.*;
public class SynchronizedListTest {
   public static void main(String[] args) {
      List<String> list = new ArrayList<String>();
      list.add("IND");
      list.add("AUS");
      list.add("WI");
      list.add("NZ");
      list.add("ENG");
      List<String> synlist = Collections.synchronizedList(list);
      synchronized(synlist) {
         Iterator<String> itr = synlist.iterator();
         while(itr.hasNext()) {
            String str = itr.next();
            System.out.println(str);
         }
      }
   }
}

Output

IND
AUS
WI
NZ
ENG

CopyOnWriteArrayList

The CopyOnWriteArrayList will create a list of the elements in the order of specified collection. It is thread-safe concurrent access of ArrayList. When an ArrayList is modified, it will create a fresh copy of the underlying array.

Syntax

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

Example

import java.util.*;
import java.util.concurrent.*;
public class CopyOnWriteArrayListTest {
   public static void main(String[] args) {
      CopyOnWriteArrayList list = new CopyOnWriteArrayList();
      list.add("Java");
      list.add("Scala");
      list.add("Python");
      list.add("Selenium");
      list.add("ServiceNow");
      System.out.println("Displaying synchronized ArrayList: ");
      Iterator itr = list.iterator();
      while(itr.hasNext()) {
         String str = itr.next();
         System.out.println(str);
      }
   }
}

Output

Displaying synchronized ArrayList:
Java
Scala
Python
Selenium
ServiceNow