import edu.princeton.cs.algs4.StdOut;
import edu.princeton.cs.algs4.Queue;
import java.util.Iterator;

public class Example4 {

    // Complete this class
    private class PeekingIterator<T> // ...
    {
        // Introduce instance variables ...
        
        public PeekingIterator(Iterator<T> it) {
            throw new RuntimeException("not implemented");
        }
        public boolean hasNext() {
            throw new RuntimeException("not implemented");
        }
        public T next() {
            throw new RuntimeException("not implemented");
        }
        public T peek() {
            throw new RuntimeException("not implemented");
        }
        public void remove() { throw new RuntimeException("not implemented"); }
    }


    public static void main(String[] args) {
        Queue<String> q = new Queue<String>();
        q.enqueue("hello");
        q.enqueue("world");
        q.enqueue("!");

        // Two ways of iterating over the objects of q.
        Iterator<String> iterator = new PeekingIterator(q.iterator());
        
        StdOut.println(iterator);
        StdOut.println(iterator.hasNext());
        StdOut.println(iterator.next());
        StdOut.println(iterator.peek());
        StdOut.println(iterator.peek());
        StdOut.println(iterator.hasNext());
        StdOut.println(iterator.next());

        // foreach loop
        for(String x : new PeekingIterator(q.iterator())) {
            StdOut.println(x);
        }
    }
    
}