Creating a tree of depth 5

[roaan]

I am doing this problem where in i have to create a tree of max depth 5. Trees of arithmetic expressions. I have classes Node, Binop, Plus, Minus, Multiply, Divide, OperatorFactory, Terminal Factory, and a main class. But what is happening currently is that the trees that are created are of some size (max 2 depth) and mostly it throws stack overflow error. To add child to the tree i have a method addRandomKids in BinOp which is supposed to add children to the trees. The code for the different classes is as follows:

[insert]

// Node.java
 
import java.util.Random;
 
/* Generated by Together */
 
public abstract class Node implements Cloneable 
{
	public int depth = 0;
    abstract void setChild(int position, Node n);
    abstract double eval(double[] data);
    
    public String toString()
    {
    	return "";
    }
    
    abstract void addRandomKids(OperatorFactory o, TerminalFactory t,int maxDepth, Random rand);
    
    public Object clone()
    {
    	Object o = null;
    	try
    	{
    		o = super.clone();
    	}
    	catch(CloneNotSupportedException e){
    		e.printStackTrace();
    	}
    	
    	return o;
    }
}
 
 
// BinOp.java
 
import java.util.Random;
 
public class Binop extends Node{
    
    protected Node lChild, rChild;
    public Binop() {}
    
    public Binop(Node l, Node r)
    {
    	lChild = l; rChild = r;
    }
   
    public void setChild(int position, Node n) 
    {
        if (position == 1)
        	lChild = n;
        else
            rChild = n;
    }
    
    public void addRandomKids(OperatorFactory o, TerminalFactory t,int maxDepth, Random rand)
    {
    	if(depth == maxDepth)
    	{
    		this.setChild(1,t.getTerminal(rand));
    		this.setChild(2,t.getTerminal(rand));
    		return;
    	}
    	else{
    		
    		int i = rand.nextInt(4);
    		if(i < 3){
    			Node lChild = o.getOperator(rand);
    			++depth;
    			lChild.addRandomKids(o, t, maxDepth, rand);
    			depth = 0;
    			Node rChild = o.getOperator(rand);
    			++ depth;
    			rChild.addRandomKids(o, t, maxDepth, rand);
    		}
    		else
    		{
    			this.setChild(1,t.getTerminal(rand));
        		this.setChild(2,t.getTerminal(rand));
        		return;
    		}
    	}
    }
 
	@Override
	double eval(double[] data) {
		// TODO Auto-generated method stub
		return 0;
	}
    
}
 
// OperatorFactory.java
 
import java.util.Random;
 
 
public class OperatorFactory {
 
	private Node[] n;
 
	OperatorFactory(Node[] node) {
		n = node;
	}
 
	public Node getOperator(Random rand) {
		Node op = null;
		int r = rand.nextInt(4);
		switch (r) {
 
		case 0:
			op = n[0];
			break;
		case 1:
			op = n[1];
			break;
		case 2:
			op = n[2];
			break;
		case 3:
			op = n[3];
			break;
		}
		return op;
	}
}
 
// TerminalFactory.java
 
import java.util.Random;
 
public class TerminalFactory {
 
	private int numIndepVars = 3;
 
	TerminalFactory(int nIndVars) {
		numIndepVars = nIndVars;
	}
 
	public Node getTerminal(Random rand) {
		
		// Choose a random number between 0 and numIndepVars
		// if less than numIndepVars return Variable else return Constant
		int r = rand.nextInt(numIndepVars)+ 1;
		if (r < numIndepVars) {
			Variable var = new Variable(r);
			return var;
		} else {
			double dble = rand.nextDouble();
			Const con = new Const(dble);
			return con;
		}
	}
}
 
// Plus.java (Same sort of files for Minus, Mult, Divide as well)
 
/* Generated by Together */
 
public class Plus extends Binop {
    public Plus() {}
    
    public Plus(Node l, Node r) {
        super(l, r);
    }
    
    public double eval(double[] data) {
        return lChild.eval(data) + rChild.eval(data);
    }
    
    public String toString() {
        String s = new String();
        s += "(" + lChild.toString() + " + " + rChild.toString() + ")";
        return s;
    }
    
}
 
// Variable.java
 
import java.util.Random;
 
/* Generated by Together */
 
public class Variable extends Node{
    private int index;
    public Variable(int i) {
        index = i;
    }
	public void setChild(int position, Node n) {
        System.out.println("Attempt to add child to Variable");
    }
    public String toString() {
        String s = new String();
        s += "X" + index;
        return s;
    }
	public double eval(double[] data) {
        if (index < data.length)
        	return data[index];
        else {
            System.out.println("Variable index exceeds data array length.");
            return 0;
        }
    }
	
	public void addRandomKids(OperatorFactory o, TerminalFactory t,int maxDepth, Random rand){}
 
}
 
// Const.java
 
import java.util.Random;
 
/* Generated by Together */
 
public class Const extends Node {
    private double value;
    public Const(double d) {value = d; }
    public void setChild(int position, Node n) {}
    public double eval(double[] data) { return value; }
    public String toString() {
        String s = new String();
        s += value;
        return s;
    }
    
    public void addRandomKids(OperatorFactory o, TerminalFactory t,int maxDepth, Random rand){}
 
}
 
 
// Main class
 
import java.util.Random;
 
public class TestAlgebra 
{
	static int numIndepVars = 3;
	static int maxDepth = 5;
	static Random rand = new Random();
	
	public static void main(String[] args) 
	{
	    double[] data = new double[3];
	    data[0] = 3.14;
	    data[1] = 2.78;
	    data[2] = 1.0;
	    
	    Node[] ops = {new Plus(), new Minus(), new Mult(),new Divide()};
	    OperatorFactory o = new OperatorFactory(ops);
	    TerminalFactory t = new TerminalFactory(numIndepVars);
	    
	    Node root = o.getOperator(rand);
	    root.addRandomKids(o, t, maxDepth, rand);
	    String s = root.toString();
	    System.out.println(s + " = " + root.eval(data));
	}
}

Also posted at:forums.sun.com/thread.jspa?threadID=5397104&tstart=0]New To Java - Creating a tree of depth 5

[mtyoung]

i find that you initialize depth to 0 in Binop.java
there should be a problem, as some other nodes will start with depth = 0