Got hit by the Comparable block again, help pls.

[niu_niu]

import java.util.*;

public class aaBSTNode <T extends Comparable<T>> {
				protected T el; 
				protected aaBSTNode<T> left, right; 
			
				public aaBSTNode( ){
				left=right=null;
				}
			
				public aaBSTNode(T el) {
				this (el, null, null); 
				}
				
				public int compareTo(Object o) {
			           	if (o instanceof aaBSTNode) {
			                      aaBSTNode temp = (aaBSTNode) o;			              
			                      	return ((temp.el) - (this.el));  
			           	} else {
			            throw new RuntimeException ("wrong class"); 
			            }
			     }
			        
				public aaBSTNode(T el, aaBSTNode<T> lt, aaBSTNode<T> rt) {
				this.el =el; left =lt; right =rt; 
				}
			
}

---------------

Hi:

I am getting an error on this line of code:

return ((temp.el) - (this.el));

The error message says: "The operator - is undefined for the argument type(s) Comparable, T". I have been trying to figure this out for days, but in vain, so some help is highly appreciated!

Niu

[Lil_Aziz1]

Why are you trying to subtract two objects? Only primitive data can use arithmetic operations.

EDIT: Some irrelevant criticism:

1. All the constructors should be together.
2. Use an IDE to write your source code (Eclipse, NetBeans, Notepad++, check out this list: What are you using to write your code? ) so the indentation isn't arbitrary.

[niu_niu]

you answer doesn't really help me.

[Singing Boyo]

you answer doesn't really help me.

Your question doesn't help us. He asked why you're trying to subtract two objects, because its not possible to do that... We don't really have enough information to help you out here...

[niu_niu]

I don't have to. I tried NULL but it doesn't work. What are my options here?

[Norm]

return ((temp.el) - (this.el));

What is this line of code supposed to do? Can you explain?

[Tolls]

Put it this way, your bit of code there is the equivalent of subtracting one Bicycle from another Bicycle.

ETA: Stab in the dark here, but are you actually supposed to be comparing the two objects, temp.el and this.el? In which case you should be doing temp.el.compareTo(this.el). Though I am a bit confused about what this class is supposed to be for...but that's another story.

[JosAH]

Put it this way, your bit of code there is the equivalent of subtracting one Bicycle from another Bicycle.

I know that one! That's a nocycle! What did I win? Am I going to be famous now?

kind regards,

Jos (<--- celebrity ;-)