Queue

Queue.java

/**
 * http://en.wikipedia.org/wiki/Queue_(data_structure)
 */
public class Queue <E> {
	private LinkedList<E> elements = new LinkedList<E>();

	public int size() { return elements.size(); }
	public boolean isEmpty() { return elements.isEmpty(); }
	public E front() { return elements.get(0); }
	public E pop() { return elements.removeFirst(); }
	public void push(E element) { elements.add(element); }
}

QueueTest.java

package org.metareal;
import junit.framework.TestCase;


public class QueueTest extends TestCase {

	public void test_empty() {
		Queue<?> queue = new Queue<Object>();
		assertNotNull(queue);
		assertTrue(queue.isEmpty());
		assertEquals(0, queue.size());
	}

	public void test_simple() {
		Queue<Integer> queue = new Queue<Integer>();
		
		queue.push(1);
		queue.push(2);
		queue.push(3);
		assertFalse(queue.isEmpty());
		assertEquals(3, queue.size());

		assertEquals(new Integer(1), queue.front());
		assertEquals(3, queue.size());

		assertEquals(new Integer(1), queue.pop());
		assertEquals(2, queue.size());
		assertEquals(new Integer(2), queue.pop());
		assertEquals(1, queue.size());
		assertEquals(new Integer(3), queue.pop());
		assertEquals(0, queue.size());
	}
	
	public void test_push_pop() {
		Queue<Integer> queue = new Queue<Integer>();
		
		queue.push(0);
		assertFalse(queue.isEmpty());
		assertEquals(1, queue.size());
		
		assertEquals(new Integer(0), queue.pop());
		assertTrue(queue.isEmpty());
		assertEquals(0, queue.size());
		
		queue.push(1);
		queue.push(2);
		assertFalse(queue.isEmpty());
		assertEquals(2, queue.size());
	}
}