Game Show Button DIY help
For something like this, you could use something like an Arduino. An Uno or Leonardo for example have through hole pins that you can hook breadboard jumpers from them to your button (you may need to buy male to female ones if the pins of the button are breadboard fit), thus removing the requirement of soldering. With some code similar to this to suit your 12 buttons (remember pull down resistors, or you could make the buttons pull the pin to logical 0 and have pinmode of the pins reading the buttons configured as INPUT_PULLUP, inverting the output), you could output serial and from the software side on the computer with the Arduino connected via USB to the computer, use your Java skills to read serial from the Arduino.