package com.kartik.tutorials;import java.util.Arrays;public class MyStackArray<E> { private int size
= 0; private static final
int DEFAULT_CAPACITY = 10; private Object
elements[]; public
MyStackArray() { elements = new
Object[DEFAULT_CAPACITY]; } public void push(E e) { if (size ==
elements.length) { ensureCapa(); }
elements[size++] = e; } @SuppressWarnings("unchecked") public E pop() { E e = (E)
elements[--size]; elements[size]
= null; return e; } private void
ensureCapa() { int newSize =
elements.length * 2; elements =
Arrays.copyOf(elements, newSize); }}
package com.kartik.tutorials;import java.util.ArrayList;public class MyStackList<E> extends
ArrayList<E> { private static final
long serialVersionUID = 1L; public E pop() { E e =
get(size() - 1); remove(size() -
1); return e; } public void
push(E e) { add(e); }}
This is a small JUnit test for the data structure.
package com.kartik.tutorials;import static org.junit.Assert.assertTrue;import org.junit.Before;import org.junit.Test;public class MyStackTest { @Before public void
setUp() throws Exception { } @Test public void
testStackArray() {
MyStackArray<Integer> stack = new MyStackArray<Integer>(); stack.push(1); stack.push(2); stack.push(3); stack.push(3); stack.push(4); assertTrue(4 ==
stack.pop()); assertTrue(3 ==
stack.pop()); assertTrue(3 ==
stack.pop()); assertTrue(2 ==
stack.pop()); assertTrue(1 ==
stack.pop()); } @Test public void
testStackList() {
MyStackList<Integer> stack = new MyStackList<Integer>(); stack.push(1); stack.push(2); stack.push(3); stack.push(3); stack.push(4); assertTrue(4 ==
stack.pop()); assertTrue(3 == stack.pop()); assertTrue(3 ==
stack.pop()); assertTrue(2 ==
stack.pop()); assertTrue(1 ==
stack.pop()); }} 
I am Kartik Chandra Mandal from Bangalore, India. Working as software engineer in Java technology. Have good knowledge of OWASP and CSRF in security for applications and it's implementation in Java technology.