Java Matrix Keypad code for use with Raspberry Pi

package application;
import java.util.HashMap;

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalMultipurpose;
import com.pi4j.io.gpio.Pin;
import com.pi4j.io.gpio.PinMode;
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;


public class CopyOfRPi_4x4_Matrix {

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

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

   /** The COLUMN pins */
   private static final Pin COLUMN_1 = RaspiPin.GPIO_04;
   private static final Pin COLUMN_2 = RaspiPin.GPIO_03;
   private static final Pin COLUMN_3 = RaspiPin.GPIO_02;
   private static final Pin COLUMN_4 = RaspiPin.GPIO_01;

   /** The Digital COLUMN 1. */
   private static GpioPinDigitalMultipurpose theCOLUMN_1 = gpio
           .provisionDigitalMultipurposePin(COLUMN_1, PinMode.DIGITAL_INPUT);

   /** The Digital COLUMN 2. */
   private static GpioPinDigitalMultipurpose theCOLUMN_2 = gpio
           .provisionDigitalMultipurposePin(COLUMN_2, PinMode.DIGITAL_INPUT);

   /** The Digital COLUMN 3. */
   private static GpioPinDigitalMultipurpose theCOLUMN_3 = gpio
           .provisionDigitalMultipurposePin(COLUMN_3, PinMode.DIGITAL_INPUT);

   /** The Digital COLUMN 4. */
   private static GpioPinDigitalMultipurpose theCOLUMN_4 = gpio
           .provisionDigitalMultipurposePin(COLUMN_4, PinMode.DIGITAL_INPUT);

   /** The Digital Column Array **/
   private final static GpioPinDigitalMultipurpose theColumns[] = {
           theCOLUMN_1,
           theCOLUMN_2,
           theCOLUMN_3,
           theCOLUMN_4
   };

   /** The ROW pins */
   private static final Pin ROW_1 = RaspiPin.GPIO_08;
   private static final Pin ROW_2 = RaspiPin.GPIO_07;
   private static final Pin ROW_3 = RaspiPin.GPIO_06;
   private static final Pin ROW_4 = RaspiPin.GPIO_05;

   /** The Digital ROW 1. */
   private static GpioPinDigitalMultipurpose theROW_1 = gpio
           .provisionDigitalMultipurposePin(ROW_1, PinMode.DIGITAL_INPUT);

   /** The Digital ROW 2. */
   private static GpioPinDigitalMultipurpose theROW_2 = gpio
            .provisionDigitalMultipurposePin(ROW_2, PinMode.DIGITAL_INPUT);

   /** The Digital ROW 3. */
   private static GpioPinDigitalMultipurpose theROW_3 = gpio
            .provisionDigitalMultipurposePin(ROW_3, PinMode.DIGITAL_INPUT);

   /** The Digital ROW 4. */
   private static GpioPinDigitalMultipurpose theROW_4 = gpio
            .provisionDigitalMultipurposePin(ROW_4, PinMode.DIGITAL_INPUT);

   /** The Digital Row Array **/
   private final static GpioPinDigitalMultipurpose theRows[] = {
           theROW_1,
           theROW_2,
           theROW_3,
           theROW_4
   };

   /** The RowId */
   private static int rowVal;

   /** The ColId */
   private static int colVal;


   /**
    * Get KEY
    */
    static void getKey() {
        // Provisioning and Set all columns as output low
        for (final GpioPinDigitalMultipurpose myTheCol : theColumns)
        {
            myTheCol.setMode(PinMode.DIGITAL_OUTPUT);
            myTheCol.setState(PinState.LOW);
        }
        // Provisioning and Set all rows as input pull-up
        for (final GpioPinDigitalMultipurpose myTheRow : theRows)
        {
            myTheRow.setMode(PinMode.DIGITAL_INPUT);
            myTheRow.setPullResistance(PinPullResistance.PULL_UP);
        }
        // Scan rows for pushed key/button
        // A valid key press should set "rowVal" between 0 and 3.
        rowVal = -1;
        for (int myR = 0; myR < theRows.length; myR++)
        {
            GpioPinDigitalMultipurpose tmpRead = theRows[myR];
            if (tmpRead.isLow())
            {
                rowVal = myR;
            }
        }
        // if rowVal is not between 0 and 3 then no button was pressed and we can exit
        if (rowVal < 0 || rowVal > 3)
        {
            exit();
        }
        // Convert columns to input pull-down
        for (final GpioPinDigitalMultipurpose myTheCol : theColumns)
        {
            myTheCol.setMode(PinMode.DIGITAL_INPUT);
            myTheCol.setPullResistance(PinPullResistance.PULL_DOWN);
        }

        // Switch the i-th row found from scan to output
        theRows[rowVal].setMode(PinMode.DIGITAL_OUTPUT);
        theRows[rowVal].setState(PinState.HIGH);

        // Scan columns for still-pushed key/button
        // A valid key press should set "colVal"  between 0 and 3.
        colVal = -1;
        for (int myC = 0; myC < theColumns.length; myC++)
        {
            GpioPinDigitalMultipurpose tmpRead = theColumns[myC];
            if (tmpRead.isHigh())
            {
                colVal = myC;
            }
        }
        // if colVal is not between 0 and 3 then no button was pressed and we can exit
        if (colVal < 0 || colVal > 3)
        {
            exit();
        }

        // Print the value of the key pressed
        exit();
        System.out.println(PINMAPPING.get(String.valueOf(rowVal)+String.valueOf(colVal)));



    } // end getKey().


     private static void exit() {
         // Reinitialize all rows and columns as input at exit
         for (final GpioPinDigitalMultipurpose myTheRow : theRows)
            {
                myTheRow.setMode(PinMode.DIGITAL_INPUT);
                myTheRow.setPullResistance(PinPullResistance.PULL_UP);
            }
         for (final GpioPinDigitalMultipurpose myTheColumn : theColumns)
            {
                myTheColumn.setMode(PinMode.DIGITAL_INPUT);
                myTheColumn.setPullResistance(PinPullResistance.PULL_UP);
            }
     }


   /**
    * Instantiates a new piezo keypad.
    */
   public CopyOfRPi_4x4_Matrix()
   {
      initMapping();
   }

   /**
        * Inits the mapping.
        *
        * Maps input/output line to key on keypad.
        */
       private void initMapping()
       {
          PINMAPPING.put("00", "1");
          PINMAPPING.put("01", "2");
          PINMAPPING.put("02", "3");
          PINMAPPING.put("01", "A");
          PINMAPPING.put("14", "4");
          PINMAPPING.put("13", "5");
          PINMAPPING.put("12", "6");
          PINMAPPING.put("11", "B");
          PINMAPPING.put("24", "7");
          PINMAPPING.put("23", "8");
          PINMAPPING.put("22", "9");
          PINMAPPING.put("21", "C");
          PINMAPPING.put("44", "*");
          PINMAPPING.put("43", "0");
          PINMAPPING.put("42", "#");
          PINMAPPING.put("41", "D");
       }
}