1import java.util.ArrayList;
2 
3class Stack<T> {
4    private ArrayList<T> items = new ArrayList<>();
5 
6    public void push(T item) {
7        items.add(item);
8    }
9 
10    public T pop() {
11        return items.remove(items.size() - 1);
12    }
13 
14    public int size() {
15        return items.size();
16    }
17}
18 
19public class Main {
20    public static void main(String[] args) {
21        Stack<String> stack = new Stack<>();
22        stack.push("a");
23        stack.push("b");
24        stack.push("c");
25        System.out.println(stack.pop());
26        System.out.println(stack.size());
27    }
28}