HW:
implement a binary tree class.

class BTree implements Comparable
{
int element;
BTree left, right;
}
it should be either comparable, or else
you should write a comparator for it.

http://en.wikipedia.org/wiki/Huffman_coding

my own lazy implementation of List-based stack
public class NodeStack<E> implements Stack<E> {
   protected SLinkedList<E> mylist;
   // protected int size; // number of elements in the stack
   public NodeStack() { // constructs an empty stack mylist = SLinkedList<E>(); }
   public int size() { return mylist.size(); }
   public boolean isEmpty() {return mylist.isEmpty()}
   public void push(E elem) {      myList.insertFront(elem);}
   public E top() throws EmptyStackException {      if (isEmpty()) throw new EmptyStackException("empty");      return mylist.front(); }
   public E pop() throws EmptyStackException {      if (isEmpty()) throw new EmptyStackException("empty");      E temp = top(); myList.removeFront();      // link-out the former top node      return temp; } }

It is better, IMHO

class MyVeryOwnComparator implements Comparator<T>
{
boolean compare(T o, T p)
{ Person per1 = (Person) }
}

class PQueue<T>
{
private Comparator<T> comp;
PQueue(Comparator<T> c)
{
comp = c;
}
void pop()
{
if(comp.compare(elem1, elem2)
}
}

main()
{
PQueue<Person>(new MyVeryOwnComparator())
}