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copied!<p>A <code>push/pop</code> operation is clearly defined for a stack abstract data type; I'm not sure if it makes sense for a queue (or even a priority queue).</p> <p><a href="http://java.sun.com/javase/6/docs/api/java/util/PriorityQueue.html" rel="nofollow noreferrer"><code>PriorityQueue</code></a><code>implements</code><a href="http://java.sun.com/javase/6/docs/api/java/util/Queue.html" rel="nofollow noreferrer"><code>Queue</code></a>, which only specifies <code>add/remove</code>. On the other hand, a <a href="http://java.sun.com/javase/6/docs/api/java/util/Deque.html" rel="nofollow noreferrer"><code>Deque</code></a> has <code>addFirst/Last</code>, <code>removeFirst/Last</code>, etc. Perhaps one of these is what you're looking for.</p> <hr> <h3>An example</h3> <p>Here's an example of using a <code>PriorityQueue</code> of <code>String</code>, using a custom <a href="http://java.sun.com/javase/6/docs/api/java/util/Comparator.html" rel="nofollow noreferrer"><code>Comparator</code></a> that compares lengths.</p> <pre><code> Queue<String> queue = new PriorityQueue<String>( 100, new Comparator<String>() { @Override public int compare(String s1, String s2) { return Integer.valueOf(s1.length()).compareTo(s2.length()); } } ); queue.add("Sally"); queue.add("Amy"); queue.add("Alice"); System.out.println(queue); // "[Amy, Sally, Alice]" System.out.println(queue.remove()); // "Amy" System.out.println(queue.remove()); // "Alice" queue.add("Tina"); System.out.println(queue.remove()); // "Tina" </code></pre> <p>As expected, the <code>PriorityQueue</code> will give the shortest <code>String</code> in the queue upon <code>remove</code>. Also as specified, ties are broken arbitrarily.</p> <h3>Related questions</h3> <p>On <code>PriorityQueue</code></p> <ul> <li><a href="https://stackoverflow.com/questions/683041/java-how-do-i-use-a-priorityqueue"> Java: How do I use a PriorityQueue? </a></li> <li><a href="https://stackoverflow.com/questions/627130/in-java-what-should-i-use-for-a-priorityqueue-that-returns-the-greatest-element-f">In Java what should I use for a PriorityQueue that returns the greatest element first?</a></li> </ul> <p>On <code>Comparator</code> and <code>Comparable</code></p> <ul> <li><a href="https://stackoverflow.com/questions/2266827/when-to-use-comparable-vs-comparator">When to use Comparable vs Comparator</a></li> <li><a href="https://stackoverflow.com/questions/1440134/java-what-is-the-difference-between-implementing-comparable-and-comparator">Java: What is the difference between implementing Comparable and Comparator?</a></li> <li><a href="https://stackoverflow.com/questions/420223/difference-between-compare-and-compareto">difference between compare() and compareTo()</a></li> <li><a href="https://stackoverflow.com/questions/2858628/comparable-and-comparator-contract-with-regards-to-null">Comparable and Comparator contract with regards to null</a></li> <li><a href="https://stackoverflow.com/questions/2892947/why-does-the-java-collections-framework-offer-two-different-ways-to-sort/">Why does the Java Collections Framework offer two different ways to sort?</a></li> </ul>

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