BlueJ (double Input)

I typed the following program using BlueJ

import static java.lang.System.out;
import java.util.Scanner;
import javax.swing.JFrame;
public class Main {
public static void main (String args[]) {
Scanner read = new Scanner (System.in);
out.print ("> ");
double num = read.nextDouble();
out.println (num);
}
}

When I compile the code it gives me no errors; however when I run the program and write a floating point number it gives me the following message:

java.util.InputMismatchException: null (in java.util.Scanner)

I used to use an online compiler and the nextDouble() method worked perfectly there.