ThreadLocalRandom Class

A java.util.concurrent.ThreadLocalRandom is a utility class introduced from jdk 1.7 onwards and is useful when multiple threads or ForkJoinTasks are required to generate random numbers. It improves performance and have less contention than Math.random() method.

ThreadLocalRandom Methods

Following is the list of important methods available in the ThreadLocalRandom class.

Example

The following TestThread program demonstrates some of these methods of the Lock interface. Here we've used lock() to acquire the lock and unlock() to release the lock.

import java.util.Random;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.ThreadLocalRandom;

public class TestThread {
  
   public static void main(final String[] arguments) {
      System.out.println("Random Integer: " + new Random().nextInt());  
      System.out.println("Seeded Random Integer: " + new Random(15).nextInt());  
      System.out.println(
         "Thread Local Random Integer: " + ThreadLocalRandom.current().nextInt());
      
      final ThreadLocalRandom random = ThreadLocalRandom.current();  
      random.setSeed(15); //exception will come as seeding is not allowed in ThreadLocalRandom.
      System.out.println("Seeded Thread Local Random Integer: " + random.nextInt());  
   }
}

This will produce the following result.

Output

Random Integer: 1566889198
Seeded Random Integer: -1159716814
Thread Local Random Integer: 358693993
Exception in thread "main" java.lang.UnsupportedOperationException
        at java.util.concurrent.ThreadLocalRandom.setSeed(Unknown Source)
        at TestThread.main(TestThread.java:21)

Here we've used ThreadLocalRandom and Random classes to get random numbers.