gistfile1.java

import edu.princeton.cs.introcs.StdOut;

import java.util.Arrays;
import java.util.Iterator;

class LinkedStack<T> implements Iterable<T> {
    private Node first;
    private int N;

    private class Node {
        T value;
        Node next;
    }

    public T pop() {
        T value = first.value;
        first = first.next;
        return value;
    }

    public void push(T item) {
        Node oldFirst = first;
        first = new Node();
        first.value = item;
        first.next = oldFirst;
        N++;
    }

    public Iterator<T> iterator() {
        return new StackIterator();
    }

    private class StackIterator implements Iterator<T> {
        private int i = N;
        private Node current = first;

        public T next() {
            T item = current.value;
            current = current.next;
            return item;
        }

        public boolean hasNext() {
            return current != null;
        }

        public void remove() {

        }
    }
}

class test {
    public static void main(String[] args) {
        LinkedStack<Integer> stack = new LinkedStack<Integer>();

        stack.push(2);
        stack.push(3);
        stack.push(4);

        int result = stack.pop();

        StdOut.print(result);

        for (int t : stack) {
            StdOut.print(t);
        }
    }
}