12 switches pressed down at the same time - does it work?

Hi there, I'm creating a switchboard with twelve switches. I've programmed it so that each switch is a key on the keyboard when not pressed and all keys are X when pressed. All twelve switches will be pressed down at the same time (key X times 12). If I stat a program that needs to react on X it won't work. Does it has anything to do with so many keys being pressed down at the same time? If so, how do I solve it?

Does it has anything to do with so many keys being pressed down at the same time?

That might depend on how the switches are wired. Or it might be a coding problem.

If so, how do I solve it?

Fix the wiring or fix the code.

The wire is OK... I'm guessing it's the code that's the problem somehow. It works fin when put in to a .jar-file, but not when it's controlling the program.

In the Java-code I've written:

 if (inputLine.equals("Button_high")) {
      try {
       Robot robot = new Robot();
       robot.keyPress(KeyEvent.VK_X);
       robot.delay(100);
       robot.keyRelease(KeyEvent.VK_X);
      } catch (AWTException e) {
       e.printStackTrace();
      }
     }

But the thing is, will this code work when X is pressed from 12 sources at the same time?

I'm guessing it's the code that's the problem somehow. It works fin when put in to a .jar-file,

How the heck do you put C++ code in a jar file?

In the Java-code I’ve written:

Where is this Java code running ?
Certainly not on the Arduino.