package me.ramswaroop.common;
import java.util.EmptyStackException;
/**
* Created by IntelliJ IDEA.
* User: ramswaroop
* Date: 3/24/15
* Time: 3:02 PM
* To change this template go to Preferences | IDE Settings | File and Code Templates
*/
/**
* Stack implementation using
* a singly linked list.
*
* @param <E>
*/
public class LinkedStack<E> implements Stack<E> {
private Node<E> top;
public LinkedStack() {
top = null;
}
/**
* Pushes an item onto the top of this stack.
*
* @param item
*/
@Override
public E push(E item) {
top = new Node<>(item, top);
return item;
}
/**
* Removes the object at the top of this stack and
* returns it.
*
* @return
*/
@Override
public E pop() {
E item = peek();
top = top.next;
return item;
}
/**
* Looks at the object at the top of this stack without removing it from the stack.
*
* @return
*/
@Override
public E peek() {
if (top == null) {
throw new EmptyStackException();
}
return top.item;
}
/**
* Returns the number of items currently in the stack.
*
* @return
*/
@Override
public int size() {
int count = 0;
for (Node node = top; node != null; node = node.next) {
count++;
}
return count;
}
/**
* Prints the content of the stack.
*/
@Override
public void print() {
Node<E> node;
System.out.print("[");
if (top == null) {
System.out.println("]");
return;
}
for (node = top; node.next != null; node = node.next) {
System.out.print(node.item + ",");
}
System.out.println(node.item + "]");
}
/**
* Tests if this stack is empty.
*
* @return
*/
@Override
public boolean isEmpty() {
return top == null;
}
private class Node<E> {
E item;
Node<E> next;
Node(E item, Node<E> next) {
this.item = item;
this.next = next;
}
}
}