"I just don't know any Java"

Me too (not really). So a i used a GUI:

Update: fixed typo.

package Perlmonks;

public class Testomato {
    
    public static void main(String[] args) {
        System.out.printf("%.49f\n",14.4);
        System.out.printf("%.49f\n", 10+14.4-10);
    }

}
[download]

I get:

14,4000000000000000000000000000000000000000000000000
14,3999999999999990000000000000000000000000000000000
[download]

Regards, Karl