package com.dataStructures;
import java.io.Serializable;
import java.util.EmptyStackException;
public class Stack implements Serializable {
/**
* Initial capacity allocated to stack on object creation
*/
private final int INITIAL_CAPACITY = 10;
/**
* Increment in memory space once stack is out of space
*/
private final int EXTENDED_CAPACITY = 10;
/**
* Position of tail in stack
*/
private int tail = -1;
/**
* Size of stack at any given time
*/
private int size;
/**
* Uninitialized array to hold stack elements.
* Will be initialized with initial capacity once the object is created
*/
private E[] elements;
/**
* No argument to create stack object with initial capacity
*/
@SuppressWarnings("unchecked")
public Stack() {
elements = (E[]) new Object[INITIAL_CAPACITY];
}
/**
* Method to check if the given stack is empty or not
*/
public boolean empty() {
return elements == null || size == 0;
}
/**
* Method to check the element on head without removing it
*/
public E peek() {
if (empty()) {
throw new EmptyStackException();
}
return elements[tail];
}
/**
* Method to remove the top element from stack
*/
public E pop() {
if (empty()) {
throw new EmptyStackException();
}
E removedElement = elements[tail];
tail--;
size--;
return removedElement;
}
/**
* Method to add element to stack
*/
@SuppressWarnings("unchecked")
public void push(E e) {
tail = tail + 1;
if (tail >= INITIAL_CAPACITY) {
E[] extendedElements = (E[]) new Object[INITIAL_CAPACITY + EXTENDED_CAPACITY];
System.arraycopy(elements, 0, extendedElements, 0, tail);
elements = extendedElements;
}
elements[tail] = e;
size = size + 1;
}
/**
* Method to search for an element in stack
*/
public int search(E o) {
int index = -1;
boolean found = false;
if (empty()) {
return -1;
}
for (int i = 0; i < size(); i++) {
if (elements[i].equals(o)) {
index = i;
found = true;
break;
}
}
if (found) {
index = tail - index + 1;
}
return index;
}
/**
* Method to get size of stack
*/
public int size() {
return size;
}
}