How to implement stack data structure in Java without using collections.
Implementing Stack without using Collections // Create interface called Stack public interface Stack { void push(Object value ); Object pop(); int length(); } // Create class implementing Stack interface named StackImpl public class StackImpl implements Stack { private Node head ; private int length ; @Override public void push(Object value ) { Node node = new Node( value ); if ( head == null ) { head = node ; } else { node . next = head ; head = node ; } length ++; } @Override public Object pop() { Object result = null ; if ( head != null ) { result = head . value ; head = head . next ; length --; } return result ; } public int length() { return length ; } private class Node { private Object value ; private Node next ; public Node(Object value ) { super (); this . value =