Lambda expressions (Project Lambda - JSR 335) are a new and important feature of the upcoming Java SE 8 platform (JSR 337). They can be used to represent one method interface (also known as functional interface) in a clear and concise way using an expression in the form of:

(argument list) -> body

In this article, we see how Lambda expressions can simplify the creation of a new thread.

 

1. Create a Java thread via Runnable using Classic Code

Before Java 8, we create and start a thread by creating an anonymous class that implements the Runnable interface, as shown in the following code:

Runnable task1 = new Runnable(){

	@Override
	public void run(){
		System.out.println("Task #1 is running");
	}
};


Thread thread1 = new Thread(task1);
thread1.start();

Or pass the anonymous class into the Thread’s constructor:

Thread thread1 = new Thread(new Runnable() {
	@Override
	public void run(){
		System.out.println("Task #1 is running");
	}
});

thread1.start();

 

2. Create a Java thread via Runnable using Lambda expression

With Lambda expressions come with Java 8, the above code can be re-written more concisely. For example:

// Lambda Runnable
Runnable task2 = () -> { System.out.println("Task #2 is running"); };

// start the thread
new Thread(task2).start();

It’s much more simple, isn’t it? By using Lambda expression, you don’t have to write the boilerplate code: declarations of the anonymous class and the run() method.

And the following code snippet is for test program that demonstrates creating threads using both classic and Lambda approaches:

package net.codejava.lambda;

/**
 * This simple program demonstrates how to use Lambda expressions to create
 * and run threads.
 *
 * @author www.codejava.net
 */
public class RunnableLambdaExample {
	public static void main(String[] args) {
		System.out.println(Thread.currentThread().getName() + ": RunnableTest");

		// Anonymous Runnable

		Runnable task1 = new Runnable(){

		  @Override
		  public void run(){
			System.out.println(Thread.currentThread().getName() + " is running");
		  }
		};


		// Passing a Runnable when creating a new thread
		Thread thread2 = new Thread(new Runnable() {
			@Override
			public void run(){
				System.out.println(Thread.currentThread().getName() + " is running");
			}
		});


		// Lambda Runnable
		Runnable task3 = () -> {
			System.out.println(Thread.currentThread().getName() + " is running");
		};

		Thread thread1 = new Thread(task1);

		thread1.start();
		thread2.start();

		new Thread(task3).start();

	}
}

Output of this program may be different on each run because there are 3 threads started simultaneously. For example:
Run #1:

main: RunnableTest
Thread-1 is running
Thread-0 is running
Thread-2 is running

Run #2:

main: RunnableTest
Thread-1 is running
Thread-2 is running
Thread-0 is running

 

Related Tutorials:

• How to use Threads in Java

 

Other Recommended Tutorials:

• 9 Rules about Constructors in Java
• 12 Rules and Examples About Inheritance in Java
• 12 Rules of Overriding in Java You Should Know
• 10 Java Core Best Practices Every Java Programmer Should Know
• Understand Interfaces in Java
• Understand Java Access Modifiers
• Understand how variables are passed in Java
• Understand Encapsulation in Java