compile java file:

javac -classpath :/opt/pi4j/lib/'*' filename.java

sync files:

git add .
git commit -m "update message"
git pull origin main
git push origin main

DIY functions:

jl_sleep(int t);

the unit of t is millisecond.
example: jl_sleep(1000); sleep 1 second

note: if we want to set high/low, need to declare the pin as "output" or "input" first!
in file: lib/JVM/std/pi7.java javac -classpath :/opt/pi4j/lib/'*' pi7.java

set_high_pi7(int pinNo);

For Raspberry Pi GPIO "output" pin. Send HIGH to Arduino;

set_low_pi7(int pinNo);

For Raspberry Pi GPIO "output" pin. Send LOW to Arduino;

get_pin_info(int pinNo);

For Raspberry Pi GPIO "input" pin. Read Arduino information.

double jl_random_1();

get a random number between 0 and 1.

int jl_random_100();

get a random integer number between 0 and 100.

Arduion:

If I set the PIN as of HIHG, the PIN will keep as HIGH until I reset it.

ProcessJ:

If I set the PIN as of HIGH, the PIN will keep as HIGH until program terminates.
Once the program terminates, all of the PINs will go back to LOW as default.