package Stack;

import org.omg.CORBA.Object;

import java.util.EmptyStackException;

public class ArrayStack<T> implements _Stack<T> {

//container

private T[] arr;

//length

private int size;

//top

private int index = -1;

private int init = 100;

public ArrayStack(int capacity) {

this.arr = (T[]) new Object[capacity];

}

public ArrayStack() {

this.arr = (T[]) new Object[this.init];

}

public int getSize() {

return this.size;

}

public void getLargeStack(int capacity) {

if (capacity < size)

return;

T[] old = this.arr;

arr = (T[]) new Object[capacity];

for (int i = 0; i < size; i++) {

arr[i] = old[i];

}

}

@Override

public boolean isEmpty() {

return this.index == -1;

}

@Override

public void push(T data) {

if (arr.length == size) {

getLargeStack(size*2 );

}

arr[index++] = data;

size++;

}

@Override

public T peek() {

if (isEmpty())

throw new NullPointerException();

return arr[index];

}

@Override

public T pop() {

if (isEmpty())

throw new NullPointerException();

size--;

return arr[index--];

}

}