Java LinkedBlockingQueue

This Java tutorial is to learn about the collection LinkedBlockingQueue which is an implementation of Java BlockingQueue. LinkedBlockingQueue order elements first-in-first-out (FIFO). With respect to bounds of the LinkedBlockingQueue, it stands in between ArrayBlockingQueue and DelayQueue.

• ArrayBlockingQueue is a bounded collection.
• DelayQueue is an unbounded collection.
• LinkedBlocingQueue is an optionally bounded collection.

LinkeBlockingQueue has an aditional constructor which provides the capability to instantiate with fixed capacity. If not the other regular argument-less constructor creates instance with Integer.MAX_VALUE capacity.

poll and offer method behaves as defined in BlockingQueue. poll method without argument retrieves the head element from the queue. poll method with timeout argument removes the head element by waiting for the time specified if the element is not available.

LinkedBlocingQueue Example

We will see a standard producer-consumer scenario example to understand the LinkeBlockingQueue.

LinkedBlockingQueueProducer.java

package com.javapapers.java.collections;

import java.util.Random;
import java.util.UUID;
import java.util.concurrent.BlockingQueue;

public class LinkedBlockingQueueProducer implements Runnable {

	protected BlockingQueue<String> blockingQueue;
	final Random random = new Random();

	public LinkedBlockingQueueProducer(BlockingQueue<String> queue) {
		this.blockingQueue = queue;
	}

	@Override
	public void run() {
		while (true) {
			try {
				String data = UUID.randomUUID().toString();
				System.out.println("Put: " + data);
				blockingQueue.put(data);
				Thread.sleep(500);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

}

LinkedBlockingQueueConsumer.java

package com.javapapers.java.collections;

import java.util.concurrent.BlockingQueue;

public class LinkedBlockingQueueConsumer implements Runnable {

	protected BlockingQueue<String> blockingQueue;

	public LinkedBlockingQueueConsumer(BlockingQueue<String> queue) {
		this.blockingQueue = queue;
	}

	@Override
	public void run() {
		while (true) {
			try {
				String data = blockingQueue.take();
				System.out.println(Thread.currentThread().getName()
						+ " take(): " + data);
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

}

LinkedBlockingQueueExample.java

package com.javapapers.java.collections;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

public class LinkedBlockingQueueExample {
	public static void main(String[] args) {
		final BlockingQueue<String> linkedBlockingQueue = new LinkedBlockingQueue<String>();

		LinkedBlockingQueueProducer queueProducer = new LinkedBlockingQueueProducer(
				linkedBlockingQueue);
		new Thread(queueProducer).start();

		LinkedBlockingQueueConsumer queueConsumer1 = new LinkedBlockingQueueConsumer(
				linkedBlockingQueue);
		new Thread(queueConsumer1).start();

		LinkedBlockingQueueConsumer queueConsumer2 = new LinkedBlockingQueueConsumer(
				linkedBlockingQueue);
		new Thread(queueConsumer2).start();

	}
}

LinkedBlockingQueue Example Output

Put: f1ef7505-6fe5-436c-893a-dd6ab8ecdba4
Thread-1 take(): f1ef7505-6fe5-436c-893a-dd6ab8ecdba4
Put: 8c86787c-a7bf-4124-b0c4-c62a195f9096
Thread-2 take(): 8c86787c-a7bf-4124-b0c4-c62a195f9096
Put: c5248f9b-17c0-41f6-a071-fecaa1dd21d3
Thread-1 take(): c5248f9b-17c0-41f6-a071-fecaa1dd21d3
Put: 05e7243e-62d4-4f32-9c9b-4b811245c571
Thread-2 take(): 05e7243e-62d4-4f32-9c9b-4b811245c571
Put: 7848bb81-a0f4-423c-b093-21db9d4412b1
Thread-1 take(): 7848bb81-a0f4-423c-b093-21db9d4412b1