4x4 Keypad Java Pi4J

package application;
import java.util.HashMap;

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalInput;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.Pin;
import com.pi4j.io.gpio.PinPullResistance;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;
import com.pi4j.io.gpio.event.GpioPinDigitalStateChangeEvent;
import com.pi4j.io.gpio.event.GpioPinListenerDigital;

/**
 * The Class PiezoKeypad.
 */
public class PiezoKeypad {

   /** The Constant PINMAPPING. */
   private static final HashMap<String, String> PINMAPPING = new HashMap<String, String>();

   /** The gpio. */
   private final GpioController theGpio = GpioFactory.getInstance();

   /** The Constant Inputs - Column */
   private static final Pin PIN_1_IN = RaspiPin.GPIO_01;
   private static final Pin PIN_2_IN = RaspiPin.GPIO_02;
   private static final Pin PIN_3_IN = RaspiPin.GPIO_03;
   private static final Pin PIN_4_IN = RaspiPin.GPIO_04;

   /** The Constant Outputs - Row */
   private static final Pin PIN_5_OUT = RaspiPin.GPIO_05;
   private static final Pin PIN_6_OUT = RaspiPin.GPIO_06;
   private static final Pin PIN_7_OUT = RaspiPin.GPIO_07;
   private static final Pin PIN_8_OUT = RaspiPin.GPIO_08;

   /** The pin1. */
   private final GpioPinDigitalInput COLUMN_1 = theGpio
         .provisionDigitalInputPin(PIN_1_IN, PinPullResistance.PULL_UP );

   /** The pin2. */
   private final GpioPinDigitalInput COLUMN_2 = theGpio
         .provisionDigitalInputPin(PIN_2_IN, PinPullResistance.PULL_UP);

   /** The pin3. */
   private final GpioPinDigitalInput COLUMN_3 = theGpio
         .provisionDigitalInputPin(PIN_3_IN, PinPullResistance.PULL_UP);

   /** The pin4. */
   private final GpioPinDigitalInput COLUMN_4 = theGpio
         .provisionDigitalInputPin(PIN_4_IN, PinPullResistance.PULL_UP);

   /** The pin5. */
   private final GpioPinDigitalOutput ROW_1 = theGpio
         .provisionDigitalOutputPin(PIN_5_OUT);

   /** The pin6. */
   private final GpioPinDigitalOutput ROW_2 = theGpio
         .provisionDigitalOutputPin(PIN_6_OUT);

   /** The pin7. */
   private final GpioPinDigitalOutput ROW_3 = theGpio
         .provisionDigitalOutputPin(PIN_7_OUT);

   /** The pin8. */
   private final GpioPinDigitalOutput ROW_4 = theGpio
         .provisionDigitalOutputPin(PIN_8_OUT);

   /** The Rows. */
   private final GpioPinDigitalOutput theOutpus[] = { ROW_1,
                                                    ROW_2,
                                                    ROW_3,
                                                    ROW_4 };

   /** The Row id. */
   private int theRowId;

   /** The Column. */
   private GpioPinDigitalInput theColumn;

   /** The Column id. */
   private int theColId;


   /**
    * Instantiates a new piezo keypad.
    */
   public PiezoKeypad()
   {
      initMapping();

      initListeners();
   }

   /**
    * Inits the listeners.
    */
   private void initListeners()
   {
      COLUMN_1.addListener(new GpioPinListenerDigital()
      {
         @Override
         public void handleGpioPinDigitalStateChangeEvent(
               final GpioPinDigitalStateChangeEvent aEvent)
         {
            if (aEvent.getState() == PinState.LOW)
            {
               theColumn = COLUMN_1;
               theColId = 1;
               findOutput();
            }
         }
      });
      COLUMN_2.addListener(new GpioPinListenerDigital()
      {
         @Override
         public void handleGpioPinDigitalStateChangeEvent(
               final GpioPinDigitalStateChangeEvent aEvent)
         {
            if (aEvent.getState() == PinState.LOW)
            {
               theColumn = COLUMN_2;
               theColId = 2;
               findOutput();;
            }
         }
      });
      COLUMN_3.addListener(new GpioPinListenerDigital()
      {
         @Override
         public void handleGpioPinDigitalStateChangeEvent(
               final GpioPinDigitalStateChangeEvent aEvent)
         {
            if (aEvent.getState() == PinState.LOW)
            {
               theColumn = COLUMN_3;
               theColId = 3;
               findOutput();
            }
         }
      });
      COLUMN_4.addListener(new GpioPinListenerDigital()
      {
         @Override
         public void handleGpioPinDigitalStateChangeEvent(
               final GpioPinDigitalStateChangeEvent aEvent)
         {
            if (aEvent.getState() == PinState.LOW)
            {
               theColumn = COLUMN_4;
               theColId = 4;
               findOutput();
            }
         }
      });
   }

   /**
    * Find output.
    *
    * Sets output lines to high and then to low one by one.
    * Then the input line is tested. If its state is low, we have the right output line and therefore
    * a mapping to a key on the keypad.
    */
   private void findOutput()
   {
       // Set all Row pins to HIGH
       for (int myO = 0; myO < theOutpus.length; myO++)
       {
         for(GpioPinDigitalOutput myTheRow : theOutpus)
         {
             myTheRow.high();;
         }
         theOutpus[myO].low();;

         // column found?
         if (theColumn.isLow())
         {
            theRowId = myO+1;
            checkPins();
            break;
         }
         for(GpioPinDigitalOutput myTheRow : theOutpus)
         {
             myTheRow.low();;
         }
      }
   }

   /**
    * Check pins.
    *
    * Determins the pressed key based on the activated GPIO pins.
    */
   private synchronized void checkPins()
   {
      if (theRowId != 0 && theColId != 0)
      {
         System.out.println("RowID:" + theRowId + " ColumnID:" + theColId);

         String key = Integer.toString(theRowId)
                     + Integer.toString(theColId);
         System.out.println("Key: " + PINMAPPING.get(key));
      }
   }

   /**
    * Inits the mapping.
    *
    * Maps input/output line to key on keypad.
    */
   private void initMapping()
   {
      PINMAPPING.put("44", "1");
      PINMAPPING.put("43", "2");
      PINMAPPING.put("42", "3");
      PINMAPPING.put("41", "A");
      PINMAPPING.put("34", "4");
      PINMAPPING.put("33", "5");
      PINMAPPING.put("32", "6");
      PINMAPPING.put("31", "B");
      PINMAPPING.put("24", "7");
      PINMAPPING.put("23", "8");
      PINMAPPING.put("22", "9");
      PINMAPPING.put("21", "C");
      PINMAPPING.put("14", "*");
      PINMAPPING.put("13", "0");
      PINMAPPING.put("12", "#");
      PINMAPPING.put("11", "D");
   }
}