[Domenic Rodriguez]

Thread.sleep() causes the current thread to pause for a time. If you call this from the main thread, the robot will be unresponsive for those 500 ms while the thread sleeps. You could avoid this by moving the solenoid code to a separate thread.

A simpler option that I often use is to record a timestamp at the start and then subtract that timestamp from future readings to get the elapsed time.

Example:

double startTime;

if (j_shooting.getRawButton(2)) {
    // This will repeatedly be set until you let go of the button
    startTime = System.currentTimeMillis(); 
} else if (j_shooting.getRawButton(1))
    // This will override, but not reset, the timer
    cyl_shoot.set(DoubleSolenoid.Value.kForward);
} else {
    // Check the time to see if the pistons should be...
    if (System.currentTimeMillis() - startTime < 0.5) {
        cyl_shoot.set(DoubleSolenoid.Value.kReverse);  // ...extended, or...
    } else {
        cyl_shoot.set(DoubleSolenoid.Value.kForward);  // ..retracted
    }
}

This way you aren't locking up the rest of your program while you wait for the pistons to retract.