Synchronized Queue

MyQueue.java

package com.xgen.svc.mms.svc.ping.observers;

import java.util.concurrent.Semaphore;

public class MyQueue {

  private Node front;
  private Node rear;
  private int numElements;
  private final int maxSize;

  private final Semaphore mutex = new Semaphore(1);

  private static class Node {
    private final Integer element;
    private Node next;

    public Node(Integer pElement) {
      this.element = pElement;
    }
  }

  public MyQueue(final int pLimit) {
    numElements = 0;
    maxSize = pLimit;
  }

  public void add(final int element) {
    try {
      mutex.acquire(); // will block until thread is available
      final Node toBeAdded = new Node(element);
      if (numElements == maxSize) {
        return;
      }
      if (rear == null) {
        rear = toBeAdded;
        front = toBeAdded;
      } else {
        rear.next = toBeAdded; // point rear to the next node
        rear = toBeAdded; // update rear to be the new node - effectively adding it to the end
      }
      numElements++;
    } catch (InterruptedException e) {
      System.out.println(e);
    } finally {
      mutex.release();
    }
  }

  public Integer get() {
    try {
      mutex.acquire();
      if (front == null) {
        return null;
      } else {
        final Node frontOfQueue = front;
        front = front.next; // updates the front of the queue
        if (front == null) {
          rear = null; // sets rear to null if queue is empty
        }
        numElements--;
        return frontOfQueue.element;
      }
    } catch (InterruptedException e) {
      System.out.println(e);
    } finally {
      mutex.release();
    }
    return null;
  }

  public int getSize() {
    try {
      mutex.acquire();
      return numElements;
    } catch (InterruptedException e) {
      System.out.println(e);
    } finally {
      mutex.release();
    }
    return -1;
  }
}