Pop
by Isai Damier, Android Engineer @ Google

/***************************************************************************
 * Author: Isai Damier
 * Title: Stack with Linked List
 *     Project: geekviewpoint
 *     Package: datastructure
 *
 * Description: Stack implementation using LinkedList
 *
 * Technical Detail:
 *    Java uses addFirst() instead of addToHead(). Also getFirst
 *    returns the head without removing it; whereas removeFirst
 *    deletes the head.
 *
 *    A single LinkedList is used to implement this
 *    stackWithLinkedList. To implement stackWithLinkedList.push(E)
 *    addFirst(E) is used; for stackWithLinkedList.pop() revomeFirst()
 *    is used; for stackWithLinkedList.peep() getFirst() is used. The
 *    trick is to remove elements from the same end they are added.
 *
 *    E is a generic that may be replaced with any actual object such
 *    as String or Integer or Object.
 **************************************************************************/ 
 import java.util.LinkedList;

public class StackWithLinkedList<E> {

  private LinkedList<E> list = new LinkedList<E>();
   
 public E pop() {
    return list.removeFirst();
  }
}

import org.junit.Test;
import static org.junit.Assert.*;

public class StackWithLinkedListTest {

 /**
   * Test of pop method, of class StackWithLinkedList.
   */
  @Test
  public void testPop() {
    System.out.println("pop");
    StackWithLinkedList<Integer> stackWithLinkedList =
            new StackWithLinkedList<Integer>();
    Integer[] inputs = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
    for (int i : inputs) {
      stackWithLinkedList.push(i);
    }
    assertFalse(stackWithLinkedList.isEmpty());
    assertEquals(inputs.length, stackWithLinkedList.size());

    for (int i = inputs.length - 1; i >= 0; i--) {
      assertEquals(inputs[i], stackWithLinkedList.pop());
    }
    assertTrue(stackWithLinkedList.isEmpty());
    assertEquals(0, stackWithLinkedList.size());
  }
}