Thread: Help creating expression tree

Hi

I need a expression tree class that conver infix expressions to postfix and prefix, and i already have this classes:

public class Stack<E>{
 
     private int d = -1;
     private int MAX = 100;
     private int size = 0;
     private E[] stack;
 
     @SuppressWarnings("unchecked")
     public Stack(int size){
          stack = (E[])new Object[size];
          this.size = size;
     }
 
     public Stack(){
          this(MAX);
     }
 
     public void push(E o) throws OverflowStackException{
          if (size == (d+1))
               throw new OverflowStackException();
 
          d++;
          stack[d] = o;
     }
 
     public E top() throws EmptyException{
          if(d == -1)
               throw new EmptyException();
          return stack[d];
     }
 
     public E pop() throws EmptyException{
          if(d == -1)
               throw new EmptyException();
          d--;
          return stack[d+1];
     }
 
     public int size(){
          return d+1;
     }
 
     public boolean empty(){
          return d == -1;
     }
 
}

public class BTree<E>{
 
     E element;
     BTree<E> dir;
     BTree<E> esq;
 
     public BTree(){
          this(null);
     }
 
     public BTree(E x){
          element = x;
          esq = null;
          dir = null;
     }
 
     public BTree(E x, BTree<E> d,  BTree<E> e){
          element = x;
          dir = d;
          esq = e;
     }
 
     public E element() throws InvalidNode{
          if(this == null)
               throw new InvalidNode("Null node");
          return element;
     }
 
     public void setElement(E x){
          element = x;
     }
 
     public void setDir(BTree<E> d){
          dir = d;
     }
 
     public void setEsq(BTree<E> e){
          esq = e;
     }
 
     public BTree<E> getDir(){
          return dir;
     }
 
     public BTree<E> getEsq(){
          return esq;
     }
 
}

and now i need that class desesperatly i didn´t get anything yet and i´m getting out of time, someone please help me??
I need to use the String Tokenizer and is all i can use from java.util.


Thanks in advance

Somebody can help me??