package com.thealgorithms.datastructures.stacks;
import java.util.ArrayList;
import java.util.EmptyStackException;
/**
* A stack implementation backed by an {@link ArrayList}, offering dynamic resizing
* and LIFO (Last-In-First-Out) behavior.
*
* <p>The stack grows dynamically as elements are added, and elements are removed
* in reverse order of their addition.
*
* @param <T> the type of elements stored in this stack
*/
public class StackArrayList<T> implements Stack<T> {
private final ArrayList<T> stack;
/**
* Constructs an empty stack.
*/
public StackArrayList() {
stack = new ArrayList<>();
}
/**
* Adds an element to the top of the stack.
*
* @param value the element to be added
*/
@Override
public void push(T value) {
stack.add(value);
}
/**
* Removes and returns the element from the top of the stack.
*
* @return the element removed from the top of the stack
* @throws EmptyStackException if the stack is empty
*/
@Override
public T pop() {
if (isEmpty()) {
throw new EmptyStackException();
}
return stack.removeLast();
}
/**
* Returns the element at the top of the stack without removing it.
*
* @return the top element of the stack
* @throws EmptyStackException if the stack is empty
*/
@Override
public T peek() {
if (isEmpty()) {
throw new EmptyStackException();
}
return stack.getLast();
}
/**
* Checks if the stack is empty.
*
* @return {@code true} if the stack is empty, {@code false} otherwise
*/
@Override
public boolean isEmpty() {
return stack.isEmpty();
}
/**
* Empties the stack, removing all elements.
*/
@Override
public void makeEmpty() {
stack.clear();
}
/**
* Returns the number of elements in the stack.
*
* @return the current size of the stack
*/
@Override
public int size() {
return stack.size();
}
}