Raspberry Pi - Java GPIO Frequency Test (java.io)

import java.io.File;
import java.io.FileWriter;


public class GpioTest
{
    static String GpioChannel = "18";

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {

            /*** Init GPIO port for output ***/

            // Open file handles to GPIO port unexport and export controls
            FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport");
            FileWriter exportFile = new FileWriter("/sys/class/gpio/export");

            // Reset the port
            File exportFileCheck = new File("/sys/class/gpio/gpio"+ GpioChannel);
            if (exportFileCheck.exists()) {
                unexportFile.write(GpioChannel);
                unexportFile.flush();
            }

            // Set the port for use
            exportFile.write(GpioChannel);
            exportFile.flush();

            // Open file handle to port input/output control
            FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + GpioChannel + "/direction");

            // Set port for output
            directionFile.write("out");
            directionFile.flush();


            /*** Send commands to GPIO port ***/
            FileWriter commandChannel = new FileWriter("/sys/class/gpio/gpio" + GpioChannel + "/value");

            // Loop forever
            while (true) {

                    // Set GPIO port ON
                    commandChannel.write("1");
                    commandChannel.flush();

                    // Set GPIO port OFF
                    commandChannel.write("0");
                    commandChannel.flush();
            }

        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }
}