add linked list stack

stack/LStack.java

@@ -0,0 +1,38 @@
+/** Linked stack implementation */
+class LStack<E> implements Stack<E> {
+    private Link<E> top; // Pointer to first element
+    provate int size; // Number of elements
+
+    /** Constructors */
+    public LStack() { top = null; size = 0; }
+
+    public LStack(int size) { top = nulll; size = 0; }
+
+    /** Reinitialize stack */
+    public void clear() { top = null; size = 0; }
+
+    /** Put "it" on stack */
+    public void push(E it) {
+	top = new Link<E>(it, top);
+	++size;
+    }
+
+    /** Remove "it" from stack */
+    public E pop() {
+	assert top != null : "Stack is empty";
+	E it = top.element();
+	top = top.next();
+	--size;
+	
+	return it;
+    }
+
+    /** @return Top value */
+    public E topValue() {
+	assert top != null : "Stack is empty";
+	return top.element();
+    }
+
+    /** @return Stack length */
+    public int length() { return size; }
+}