Something

import a4.Parser;
import a4.SymbolTable;
import a4.MalformedExpressionException;
import a4.NoSuchVariableException;

public abstract class ExpressionTree {
  ExpressionTree parent;
  ExpressionTree leftChild;
  ExpressionTree rightChild;
  String data;
  // Static CreateTree Method
  public static ExpressionTree createTree(Parser tokens) {
    return(createNode(tokens,null));
  }
  // ********************************************************************************************
  // ********************************************************************************************
  // ********************************************************************************************
  // ********************************************************************************************
  public static ExpressionTree createNode(Parser tokens, ExpressionTree parent) {
    // Check if we have a next token or else return null
    String curItem;
    if (tokens.hasNext()) {
      curItem = tokens.next();
      if (curItem.equals("(")) {
        createNode(tokens,null);
        System.out.println("Returning: "+parent);
        return(parent);
      }
      System.out.println("New curItem: "+curItem);
    } else {
      curItem = "";
    }
    // Creating a root node, should only happen once
    if (parent == null && !curItem.equals("")) {
      System.out.println("*** case zero ***");
      ExpressionTree firstNode = new IntTerm(null,tokens,curItem);
      createNode(tokens,firstNode);
      return(firstNode); // return the root node to createTree after everything is done
    } else {
      // Check for types
      if (curItem.equals("@b+")) {
        parent = new AddExp(parent.parent,tokens,curItem,parent);
        // Swap parent
        createNode(tokens,parent);
        createNode(tokens,parent.rightChild);
        return(parent);
      } else if (curItem.equals("(")) {
        System.out.println("( reached, P:"+parent);
        createNode(tokens,parent); // keep going to next, we don't care about (
      } else if (curItem.equals(")")) {
        if (parent.parent != null) {
          System.out.println("*** MIDDLEGROUND");
          ExpressionTree middleGround = null;
          System.out.println(parent.parent.leftChild+" (parent.parent.leftChild) ---> MiddleGround");
          parent.parent.leftChild = middleGround;
          System.out.println(parent.parent+" (parent.parent) ---> MiddleGround");
          parent.parent = middleGround;
          middleGround = createNode(tokens,parent.parent);
          System.out.println("MiddleGround = "+middleGround);
          createNode(tokens,parent);
        } else {
           parent.parent = new AddExp(null,tokens,curItem,parent.parent);
        }
      } else {
        if (!curItem.equals("")) {
          if (parent instanceof BinaryExp) {
            parent.rightChild = new IntTerm(parent,tokens,curItem);
            return(parent);
          } else {
            parent.leftChild = new IntTerm(parent,tokens,curItem);
            return(parent);
          }
        } else {
          System.out.println("Returning itself to P:"+parent);
          return(parent);
        }
      }
      System.out.println("Returning parent to P:"+parent);
      return(parent);
    }
  }
  // ********************************************************************************************
  // ********************************************************************************************
  // ********************************************************************************************
  // ********************************************************************************************
  // PRINTOUT METHOD FOR TESTING ONLY
  public void printOut() {
    if (leftChild != null && rightChild != null) {
      System.out.println("["+data+"] ("+this+") L:"+leftChild.data+" R:"+rightChild.data + " P:"+parent);
      leftChild.printOut();
      rightChild.printOut();
    } else if (leftChild != null && rightChild == null) {
      System.out.println("["+data+"] ("+this+") L:"+leftChild.data+" R:null" + " P:"+parent);
      leftChild.printOut();
    } else if (leftChild == null && rightChild != null) {
      System.out.println("["+data+"] ("+this+") L:null R:"+rightChild.data + " P:"+parent);
      rightChild.printOut();
    } else {
      System.out.println("["+data+"] ("+this+") L:null R:null" + " P:"+parent);
    }
  }
  //public abstract String toString();

  //public abstract boolean isWellFormed();

  //public abstract int eval(SymbolTable sym);

  //public abstract ExpressionTree copy();

  //public abstract ExpressionTree simplify();

}