Exception on a simple size converter

[Dado]

Hello everyone.
I'm relatively new to java and i'm studying it at school at the moment. As the thread name implies, i'm trying to create a small size converter, but there's a problem with the item listener assigned to the choice menu. After selecting another option it should update the string to the new value, but the string keeps a null value.What am i doing wrong? am i forgetting something around? i really can't see where's the error..

EDIT: sorry, didn't know that :o first time on a forum like this.
Well, i don't know where the error is, but it's probably inside the ConvertListener, so i'll just tag that one.

import java.awt.*;
import java.awt.event.*;
import java.lang.*;
class ConvertListener implements ActionListener,ItemListener{
	private TextField t_in;
	private TextField t_out;
	private String s;
	private double value;
	private float v;
	public ConvertListener(TextField t_in, TextField t_out){
		this.t_in=t_in;
		this.t_out=t_out;
	}
	public void itemStateChanged(ItemEvent e){
		Object x=e.getItem();
		s=x.toString();
		System.out.println(s);
	}
	public void actionPerformed(ActionEvent e){
		String tb=e.getActionCommand();
		System.out.println("s---->"s);
		System.out.println(tb);
		if(tb.equals("Cancel")){
			t_in.setText("");
			t_out.setText("");
		}
		else if(tb.equals("Convert")){
			System.out.println("Inside Convert");
			value=Double.parseDouble(t_in.getText());
			if(s.equals("Meters")){
			System.out.println("Inside Meters");
				value=value;
			}
			else if(s.equals("Decimeters")){
			System.out.println("Inside Decimeters");
				value=value/10;
			}
			else if(s.equals("Centimeters")){
			System.out.println("Inside Centimeters");
				value=value/100;
			}
			else if(s.equals("Millimeters")){
			System.out.println("Inside Millimeters");
				value=value/1000;
			}
			else {
				System.out.println("Always get here");


			}
			t_out.setText(Double.toString(value));
		}
	}
}

System.out lines are for debugging purposes :)
Thanks in advance for any help

[Nadian]

I made the mistake of attaching my code to my question, but its not a good thing to do. You need to use the CODE tag. When writing the message, copy and paste the code in then select it and click in the Wrap code (#) button, this quotes the code nicely in the main thread.I don't think people will look at your code otherwise.

[Dado]

sorry for doubleposting, i edited it and i'm bumping it to top.