StacksLinked.java

public class StacksLinked {
	  class Node {
	        int element;
	        Node next;
	        public Node(int e, Node n) {
	            element = e;
	            next = n;
	        }
	    }

	    private Node top;
	    private int size;

	    public StacksLinked() {
	        top = null;
	        size = 0;
	    }

	    public int length() {
	        return size;
	    }

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

	    public void push(int e) {
	        Node newest = new Node(e, null);
	        if(isEmpty()) {
	            top = newest;
	        }
	        else {
	            newest.next = top;
	            top = newest;
	        }
	        size = size + 1;
	    }

	    public int pop() {
	        if(isEmpty()) {
	            System.out.println("Stack is Empty");
	            return -1;
	        }
	        int e = top.element;
	        top = top.next;
	        size = size - 1;
	        return e;
	    }

	    public int peek() {
	        if(isEmpty()) {
	            System.out.println("Stack is Empty");
	            return -1;
	        }
	        return top.element;
	    }

	    public void display() {
	        Node p = top;
	        while(p!=null) {
	            System.out.print(p.element + "-->");
	            p = p.next;
	        }
	        System.out.println();
	    }

	    public static void main(String args[]) {
	        StacksLinked s = new StacksLinked();
	        s.push(5);
	        s.push(3);
	        s.display();
	        System.out.println("size: " + s.length());
	        System.out.println("Element Popped: " + s.pop());
	        System.out.println("IsEmpty: " + s.isEmpty());
	        System.out.println("Element Popped: " + s.pop());
	        System.out.println("IsEmpty: " + s.isEmpty());
	        s.push(7);
	        s.push(9);
	        s.display();
	        System.out.println("Element Top: " + s.peek());
	        s.display();
	    }
}