Type Safe Classes

We always try to use type safe collections where ever possible, for example
<br />List<String> list = new ArrayList<String>();<br />
What would it take to implement a type safe Collection like Stack ? Below is the implementation of type safe Stack class
<br />public class Stack<E> {<br /> private E[] elements;<br /> private int size = 0;<br /> private static final int INITIAL_CAPACITY = 16;<br /> private static final int INCREMENTAL = 10;<br /> <br /> @SuppressWarnings("unchecked")<br /> public Stack(){<br /> /* problem here is we cannot create new E[], we'll always get into<br /> * these issues if we try to use generics with arrays.<br /> */<br /> elements = (E[]) new Object[INITIAL_CAPACITY];<br /> }<br /> public void push(E element){<br /> ensureCapacity();<br /> elements[size++] = element;<br /> }<br /> public E pop(){<br /> if (size == 0)<br /> throw new EmptyStackException();<br /> E result = elements[--size];<br /> elements[size] = null;<br /> return result;<br /> }<br /> public boolean isEmpty(){<br /> return size == 0;<br /> }<br /> @SuppressWarnings("unchecked")<br /> private void ensureCapacity(){<br /> if (elements.length == size){<br /> E[] oldData = elements;<br /> int length = elements.length;<br /> elements = (E[]) new Object[elements.length + INCREMENTAL];<br /> System.arraycopy(oldData, 0, elements, 0, length);<br /> }<br /> }<br />}<br />

Why I have used "@SuppressWarnings("unchecked")", and still claiming it to be type safe ? First, its type safe for the client using this Stack, its pushes and pops element of type E. Second, we know what we are doing, we are typecasting Object[] to E[]; hence a "@SuppressWarnings("unchecked")."

<br />Stack<String> stack = new Stack<String>();<br />stack.push("one");<br />stack.push("two");<br /><br />//no type cast required<br />String element = stack.pop();<br />