LinkedStack.java

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/**
 *
 * @author Ragha
 */
public class LinkedStack<E> {

    private Node<E> top;
    private int size;

    public LinkedStack() {
        top = null;
        size = 0;
    }
    public LinkedStack(Node node) {
        top = node;
        size = 0;
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public void push(E data) {
// Make a new node whose next reference is the existing list
        Node<E> newNode = new Node(data, top);
        top = newNode; // top points to new node
        size++;
    }

    public E pop() {
        if(top == null)
        return null;
        
        E t = top.data; // Save the value at the top of the stack
        top = top.next; // Make top reference points to the next node in the stack
        size--;
        
        return t; // return the removed value
    }

    public E top() {
        if(top == null)
        return null;
        
        return top.data;
    }

}