Generics Question

[erversteeg]

Okay so I've been writing a Binary Search Tree for school and have run into a problem.

My BST class is generic and in one of my methods I need to compare data in nodes to find their place in the tree.

The problem is that when I compile my main class it says "cannot find symbol method compareTo(java.lang.Object)". How can I tell my BinarySearchTree class to only accept generic types that implement Comparable?

These are my classes.

public class BinarySearchTree<T> {
        
	BTNode root;
	
	public void insert(T obj){
		BTNode node = new BTNode<T>(obj);
		
		if(root == null){
			root = node;
			System.out.println("hmm");
		}
		else{
			if(obj.compareTo(root.getData()) > 0){
				System.out.println("Yay");
			}
			else{
				System.out.println("yay2");
			}
		}
	}
}

public class BTNode<T> {

    T data;
    BTNode left;
    BTNode right;
    
    public BTNode(T obj){
    	data = obj;
    }
    
    public void setData(T obj){
    	data = obj;
    }  
    
    public T getData(){
    	return data;
    }
    
    public void setLeft(BTNode node){
    	left = node;
    }
    
    public BTNode getLeft(){
    	return left;
    }
    
    public void setRight(BTNode node){
    	right = node;
    }
    
    public BTNode getRight(){
    	return right;
    }
}

public class Index implements Comparable<Index>{
	
	int pos;
	String ssn;
	
    public Index(String ssNum, int i) {
    	ssn = ssNum;
    	pos = i;
    }
    
    public int compareTo(Index index){
    	return ssn.compareTo(index.getSSN());
    }
    
    public int getIndex(){
    	return pos;
    }
    
    public String getSSN(){
    	return ssn;
    }
    
}

public class DatabaseMain {

    public static void main(String [] args){
    	BinarySearchTree<Index> bst = new BinarySearchTree<Index>();
    	
    	bst.insert(new Index("003436857", 0));
    	bst.insert(new Index("112576757", 1));
    }   
}

[Fubarable]

Get your T to extend Comparable<T>

class BinarySearchTree<T extends Comparable<T>> {

Your other classes that are generic should do the same, and you will need to "genericize" the declaration of your fields of these classes that need it. i.e.,

class BinarySearchTree<T extends Comparable<T>> {

   BTNode<T> root;  // don't forget generics here as well.

[erversteeg]

It worked! Thanks Fubarable!

[Fubarable]

You're welcome.