Não estou conseguindo usar ResourceBundle

package teste;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ResourceBundle;

public class TesteResourceBundle {
	public static void main(String[] args) {
		ResourceBundle resourceBundle;
		resourceBundle = ResourceBundle.getBundle("res/Teste");
		System.out.println(resourceBundle.getString("mensagens.mensagem"));
		BufferedReader reader = new BufferedReader(new InputStreamReader(
				System.in));
		try {
			String n = reader.readLine();
			double d = Double.parseDouble(n);
			if (d < 0) {
				System.out.println(resourceBundle
						.getString("mensagens.negativo"));
			} else {
				System.out.println(resourceBundle
						.getString("mensagens.positivo"));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}