Generic Stack Implementation in Java

Stack.java

class Stack<T> implements Stackable<T> {
	private Stack<T> previous;
	private T value;

	Stack() {
	}

	Stack(T value) {
		this.value = value;
	}

	Stack(Stack<T> previous, T value) {
		this.previous = previous;
		this.value = value;
	}

	@Override
	public void push(T value) {
		if (this.value == null)
			this.value = value;
		else {
			this.previous = new Stack<T>(this.previous, this.value);
			this.value = value;   
		}
	}

	@Override
	public T pop() {
		if (this.isEmpty())
			throw new IllegalArgumentException("Stack is empty");

		T top = this.value;
		this.value = this.previous.value;
		this.previous = this.previous.previous;

		return top;
	}

	@Override
	public T peek() {
		return this.value;
	}

	@Override
	public boolean isEmpty() {
		return this.previous == null;
	}

	@Override
	public int size() {
		return this.isEmpty() ? 0 : 1 + this.previous.size();
	}

	@Override
	public int search(Object o) {
		int count = 1;

		for (Stack<T> stack = this; !stack.isEmpty(); stack = stack.previous) {
			if (stack.value.equals(o))
				return count;
			count++;
		}

		return -1;
	}

	@Override
	public String toString() {
		if (!this.isEmpty())
			return this.previous + " <- " + this.value;
		return this.value != null ? String.valueOf(this.value) : "";
	}
}

Stackable.java

interface Stackable<T> {
	void push(T value);
	T pop();
	T peek();
	boolean isEmpty();
	int size();
	int search(Object o);
}

Smart, simple and efficient solution, I like it, thanks! :)