This example demonstrate how to use the PriorityBlockingQueue class. The PriorityBlockingQueue is one implementation of the BlockingQueue interface. It is an unbounded concurrent queue. The object place in this type of queue must implements the java.lang.Comparable interface. The Comparable interface defines how the order priority of the elements inside this queue.

For simplicity, in this example we use strings object as the elements to be placed in the queue. The String class implements the comparable interface. When we run this example it will print out the names in the string array in alphabetical orders.

package org.kodejava.example.util.concurrent;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.PriorityBlockingQueue;

public class PriorityBlockingQueueExample {
    public static void main(String[] args) {
        final String[] names =
                {"carol", "alice", "malory", "bob", "alex", "jacobs"};

        final BlockingQueue<String> queue = new PriorityBlockingQueue<>();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < names.length; i++) {
                    try {
                        queue.put(names[i]);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "Producer").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    for (int i = 0; i < names.length; i++) {
                        System.out.println(queue.take());
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Consumer").start();
    }
}

This code print out:

alex
alice
bob
carol
jacobs
malory

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Wayan Saryada

Programmer, runner, recreational diver, currently living in the island of Bali, Indonesia. Mostly programming in Java, creating web based application with Spring Framework, Hibernate / JPA.

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