JavaでもGPIOを弄れるらしい。すごい。
http://pi4j.com/example/control.html


ということで Javaインストール

$ sudo apt-get install openjdk-7-jdk

$ java -version
java version "1.7.0_25"
OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1~deb7u1+rpi1)
OpenJDK Zero VM (build 22.0-b10, mixed mode)

$ javac -version
javac 1.7.0_25

$ vi HelloJava.java
public class HelloJava{
　 public static void main(String[] argv){
　 　 System.out.println("Hello Rpi in java");
　 }
}

$ javac HelloJava.java
$ java HelloJava
Hello Rpi in java


次はpi4jの取得

$ mkdir pi4j
$ cd pi4j
$ http://pi4j.googlecode.com/files/pi4j-1.0-SNAPSHOT.zip
$ unzip pi4j-1.0-SNAPSHOT.zip

以下のサンプルを　ControlGpioExample.java として保存します。

/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  ControlGpioExample.java  
 * 
 * This file is part of the Pi4J project. More information about 
 * this project can be found here:  http://www.pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2013 Pi4J
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;

/**
 * This example code demonstrates how to perform simple state
 * control of a GPIO pin on the Raspberry Pi.  
 * 
 * @author Robert Savage
 */
public class ControlGpioExample {
    
    public static void main(String[] args) throws InterruptedException {
        
        System.out.println("<--Pi4J--> GPIO Control Example ... started.");
        
        // create gpio controller
        final GpioController gpio = GpioFactory.getInstance();
        
        // provision gpio pin #01 as an output pin and turn on
        final GpioPinDigitalOutput pin = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_01, "MyLED", PinState.HIGH);
        System.out.println("--> GPIO state should be: ON");
        
        Thread.sleep(5000);
        
        // turn off gpio pin #01
        pin.low();
        System.out.println("--> GPIO state should be: OFF");

        Thread.sleep(5000);

        // toggle the current state of gpio pin #01 (should turn on)
        pin.toggle();
        System.out.println("--> GPIO state should be: ON");

        Thread.sleep(5000);

        // toggle the current state of gpio pin #01  (should turn off)
        pin.toggle();
        System.out.println("--> GPIO state should be: OFF");
        
        Thread.sleep(5000);

        // turn on gpio pin #01 for 1 second and then off
        System.out.println("--> GPIO state should be: ON for only 1 second");
        pin.pulse(1000, true); // set second argument to 'true' use a blocking call
        
        // stop all GPIO activity/threads by shutting down the GPIO controller
        // (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
        gpio.shutdown();
    }
}

コンパイル、実行してみる

$ javac -cp .:pi4j/pi4j-1.0-SNAPSHOT/lib/* ControlGpioExample.java
$ sudo java -cp .:pi4j/pi4j-1.0-SNAPSHOT/lib/* ControlGpioExample

無事チカチカさせることに成功。