依照教材，我直接在相關網站下載了RXTXcomm的相關包：Download - Rxtx (qbang.org)

在Ubuntu裡面，將 librxtxParallel.so  librxtxSerial.so 拷貝到jre資料夾下的 lib/amd64/裡面

然後拷貝 RXTXcomm.jar 到jre資料夾下的 lib//ext 裡面

寫程式碼：略（網上一抓一大把，有空補充，如果有人問的話）

執行jar包後報錯：

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f84ae95e733
 
, pid=8075, tid=0x00007f84ae855700
#
# JRE version: Java(TM) SE Runtime Environment (8.0_281-b09) (build 1.8.0_281-b09)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.281-b09 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# C  [librxtxSerial.so+0x7733]  Java_gnu_io_RXTXPort_nativeDrain+0xc3
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, 
 
try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/boocax/download/hs_err_pid8075.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in
 
 native code.
# See problematic frame for where to report the bug.
#
已放棄 (核心已轉儲)

解決辦法：

  sudo apt-get install librxtx-java 

 在： /urs/lib/jni/  資料夾中找到新的 lib,  librxtxParallel.so  和  librxtxSerial.so 拷貝到 jre資料夾下的 lib/amd64/ 裡面