Pi4J(外链网址已屏蔽)是专门用来控制树莓派GPIO口以及通信的Java库。它有如下功能：

Export & unexport GPIO pins

Configure GPIO pin direction

Configure GPIO pin edge detection

Control/write GPIO pin states

Pulse GPIO pin state

Read GPIO pin states

Listen for GPIO pin state changes (interrupt-based; not polling)

Automatically set GPIO states on program termination (GPIO shutdown)

Triggers for automation based on pin state changes

Send & receive data via RS232 serial communication

I2C Communication

SPI Communication

Extensible GPIO Provider interface to add GPIO capacity via expansion boards

Access system information and network information from the Raspberry Pi

Wrapper classes for direct access to WiringPi Library from Java

下载、新手帮助、API文档均可从官网找到。