Building with javac

You can build a Pi4J project using only java and javac.

Wiring

No wiring is needed for this minimal example as it only demonstrates how to create a minimal application which initializes Pi4J.

Java release

Any Java release over 11 is enough, check it with this command:

$ java -version
java 17.0.1 2021-10-19 LTS
Java(TM) SE Runtime Environment (build 17.0.1+12-LTS-39)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.1+12-LTS-39, mixed mode, sharing)

PI4J jar files

You will need to download the Pi4J distribution from the Maven repository:

pi4j-distribution-2.1.1.zip

Expand the file:

unzip pi4j-distribution-2.1.1.zip

Add the lib directory to CLASSPATH by added this line to your .bashrc file:

export CLASSPATH=$CLASSPATH:~/pi4j-2.1.1/lib/*

Minimal Java example file

Use your preferred editor to create this GettingStartedExample.java file:

import com.pi4j.Pi4J;
import com.pi4j.io.gpio.digital.DigitalOutput;
import com.pi4j.platform.Platform;
import com.pi4j.platform.Platforms;
import com.pi4j.provider.Providers;
import com.pi4j.registry.Registry;
import com.pi4j.util.Console;

public class GettingStartedExample {

    public static void main(String[] args) throws Exception {

        final var console = new Console();

        console.title("<-- The Pi4J Project -->", "Getting Started Example");

        var pi4j = Pi4J.newAutoContext();

        Platforms platforms = pi4j.platforms();

        console.box("Pi4J PLATFORMS");
        platforms.describe().print(System.out);
        console.println();

        Platform platform = pi4j.platform();

        console.box("Pi4J DEFAULT PLATFORM");
        platform.describe().print(System.out);
        console.println();

        Providers providers = pi4j.providers();
        console.box("Pi4J PROVIDERS");
        providers.describe().print(System.out);
        console.println();

        Registry registry = pi4j.registry();

        DigitalOutput output = pi4j.dout().create(1, "my-digital-output-1");

        console.box("Pi4J REGISTRY");
        registry.describe().print(System.out);
        console.println();

        pi4j.shutdown();
    }
}

Compile the example

javac GettingStartedExample.java

Execute the example

java GettingStartedExample

If everything is OK the output must be something similar to this, depending on your configuration:

[main] INFO com.pi4j.util.Console - 

[main] INFO com.pi4j.util.Console - ************************************************************
[main] INFO com.pi4j.util.Console - ************************************************************
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.util.Console -                   <-- The Pi4J Project -->                  
[main] INFO com.pi4j.util.Console -                    Getting Started Example                  
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.util.Console - ************************************************************
[main] INFO com.pi4j.util.Console - ************************************************************
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.Pi4J - New auto context
[main] INFO com.pi4j.Pi4J - New context builder

[main] INFO com.pi4j.platform.impl.DefaultRuntimePlatforms - adding platform to managed platform map [id=raspberrypi; name=RaspberryPi Platform; priority=5; class=com.pi4j.plugin.raspberrypi.platform.RaspberryPiPlatform]
[main] INFO com.pi4j.util.Console - --------------------
[main] INFO com.pi4j.util.Console - |  Pi4J PLATFORMS  |
[main] INFO com.pi4j.util.Console - --------------------
PLATFORMS: [1] "Pi4J Runtime Platforms" <com.pi4j.platform.impl.DefaultPlatforms> 
??PLATFORM: "RaspberryPi Platform" {raspberrypi} <com.pi4j.plugin.raspberrypi.platform.RaspberryPiPlatform> {Pi4J Platform for the RaspberryPi series of products.} 
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.util.Console - ---------------------------
[main] INFO com.pi4j.util.Console - |  Pi4J DEFAULT PLATFORM  |
[main] INFO com.pi4j.util.Console - ---------------------------
PLATFORM: "RaspberryPi Platform" {raspberrypi} <com.pi4j.plugin.raspberrypi.platform.RaspberryPiPlatform> {Pi4J Platform for the RaspberryPi series of products.} 
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.util.Console - --------------------
[main] INFO com.pi4j.util.Console - |  Pi4J PROVIDERS  |
[main] INFO com.pi4j.util.Console - --------------------
PROVIDERS: [12] "I/O Providers" <com.pi4j.provider.impl.DefaultProviders> 
??DIGITAL_INPUT: [2] <com.pi4j.io.gpio.digital.DigitalInputProvider> 
? ??PROVIDER: "RaspberryPi Digital Input (GPIO) Provider" {raspberrypi-digital-input} <com.pi4j.plugin.raspberrypi.provider.gpio.digital.RpiDigitalInputProviderImpl> {com.pi4j.plugin.raspberrypi.provider.gpio.digital.RpiDigitalInputProviderImpl} 
? ??PROVIDER: "PiGpio Digital Input (GPIO) Provider" {pigpio-digital-input} <com.pi4j.plugin.pigpio.provider.gpio.digital.PiGpioDigitalInputProviderImpl> {com.pi4j.plugin.pigpio.provider.gpio.digital.PiGpioDigitalInputProviderImpl} 
??SERIAL: [2] <com.pi4j.io.serial.SerialProvider> 
? ??PROVIDER: "RaspberryPi Serial Provider" {raspberrypi-serial} <com.pi4j.plugin.raspberrypi.provider.serial.RpiSerialProviderImpl> {com.pi4j.plugin.raspberrypi.provider.serial.RpiSerialProviderImpl} 
? ??PROVIDER: "PiGpio Serial Provider" {pigpio-serial} <com.pi4j.plugin.pigpio.provider.serial.PiGpioSerialProviderImpl> {com.pi4j.plugin.pigpio.provider.serial.PiGpioSerialProviderImpl} 
??PWM: [2] <com.pi4j.io.pwm.PwmProvider> 
? ??PROVIDER: "PiGpio PWM Provider" {pigpio-pwm} <com.pi4j.plugin.pigpio.provider.pwm.PiGpioPwmProviderImpl> {com.pi4j.plugin.pigpio.provider.pwm.PiGpioPwmProviderImpl} 
? ??PROVIDER: "RaspberryPi PWM Provider" {raspberrypi-pwm} <com.pi4j.plugin.raspberrypi.provider.pwm.RpiPwmProviderImpl> {com.pi4j.plugin.raspberrypi.provider.pwm.RpiPwmProviderImpl} 
??I2C: [2] <com.pi4j.io.i2c.I2CProvider> 
? ??PROVIDER: "PiGpio I2C Provider" {pigpio-i2c} <com.pi4j.plugin.pigpio.provider.i2c.PiGpioI2CProviderImpl> {com.pi4j.plugin.pigpio.provider.i2c.PiGpioI2CProviderImpl} 
? ??PROVIDER: "RaspberryPi I2C Provider" {raspberrypi-i2c} <com.pi4j.plugin.raspberrypi.provider.i2c.RpiI2CProviderImpl> {com.pi4j.plugin.raspberrypi.provider.i2c.RpiI2CProviderImpl} 
??ANALOG_OUTPUT: [0] <com.pi4j.io.gpio.analog.AnalogOutputProvider> 
??SPI: [2] <com.pi4j.io.spi.SpiProvider> 
? ??PROVIDER: "PiGpio SPI Provider" {pigpio-spi} <com.pi4j.plugin.pigpio.provider.spi.PiGpioSpiProviderImpl> {com.pi4j.plugin.pigpio.provider.spi.PiGpioSpiProviderImpl} 
? ??PROVIDER: "RaspberryPi SPI Provider" {raspberrypi-spi} <com.pi4j.plugin.raspberrypi.provider.spi.RpiSpiProviderImpl> {com.pi4j.plugin.raspberrypi.provider.spi.RpiSpiProviderImpl} 
??DIGITAL_OUTPUT: [2] <com.pi4j.io.gpio.digital.DigitalOutputProvider> 
? ??PROVIDER: "RaspberryPi Digital Output (GPIO) Provider" {raspberrypi-digital-output} <com.pi4j.plugin.raspberrypi.provider.gpio.digital.RpiDigitalOutputProviderImpl> {com.pi4j.plugin.raspberrypi.provider.gpio.digital.RpiDigitalOutputProviderImpl} 
? ??PROVIDER: "PiGpio Digital Output (GPIO) Provider" {pigpio-digital-output} <com.pi4j.plugin.pigpio.provider.gpio.digital.PiGpioDigitalOutputProviderImpl> {com.pi4j.plugin.pigpio.provider.gpio.digital.PiGpioDigitalOutputProviderImpl} 
??ANALOG_INPUT: [0] <com.pi4j.io.gpio.analog.AnalogInputProvider> 
[main] INFO com.pi4j.util.Console - 
[main] INFO com.pi4j.util.Console - -------------------
[main] INFO com.pi4j.util.Console - |  Pi4J REGISTRY  |
[main] INFO com.pi4j.util.Console - -------------------
REGISTRY: [1] "I/O Registered Instances" <com.pi4j.registry.impl.DefaultRegistry> 
??IO: "DOUT-1" {my-digital-output-1} <com.pi4j.plugin.raspberrypi.provider.gpio.digital.RpiDigitalOutput> {DOUT-1} 
[main] INFO com.pi4j.util.Console -

Thanks to Manuel de Vega Barreiro for this contribution.