Stack

Stack.java

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

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

StackTest.java

import junit.framework.TestCase;


public class StackTest extends TestCase {

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

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

		assertEquals(new Integer(3), stack.top());
		assertEquals(3, stack.size());

		assertEquals(new Integer(3), stack.pop());
		assertEquals(2, stack.size());
		assertEquals(new Integer(2), stack.pop());
		assertEquals(1, stack.size());
		assertEquals(new Integer(1), stack.pop());
		assertEquals(0, stack.size());
	}
}