Stacks

import java.util.ArrayList;

public class Stack<T> {
    private ArrayList<T> stack;
    
    public Stack() {
        stack = new ArrayList<>();
    }

    public void push(T item) {
        stack.add(item);
    }

    public T pop() {
        return stack.remove(stack.size() - 1);
    }

    public boolean isEmpty() {
        return stack.isEmpty();
    }

    public int size() {
        return stack.size();
    }

    public String toString(){
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("[");
        for (int i = 0; i < stack.size(); i++) {
            stringBuilder.append(stack.get(i));
            if (i != stack.size() - 1) {
                stringBuilder.append(", ");
            }
        }
        stringBuilder.append("]");
        return stringBuilder.toString();
    }
}

class Main{
    public static void main(String[] args){
        Stack<Integer> Stack = new Stack();
        Stack.push(3);
        Stack.push(4);
        Stack.push(5);
        System.out.println(Stack);

        System.out.println(Stack.size());
        System.out.println("popped this: " + Stack.pop());
        System.out.println(Stack);

    }
}

Main.main(null);

[3 4 5]
3
popped this: 5
[3 4]