Upfront disclosure: I am not a Java programmer, but am slowly picking it up.

I am following https://kunlei.github.io/cplex/cplex-java-setup to compile an example that uses CPLEX's Java API. I'm on Windows 10, but because of my familiarity with Cygwin's Bash and Gvim, I use them to get around and manipulate files. I may complement them with an IDE down the road. For now, the compiler is invoked using:

javac -Xstdout mk.out \

-classpath \

'c:/Program Files/IBM/ILOG/CPLEX_Studio129/cplex/lib/cplex.jar' \

TestSetup.java

For the JDK, I have AdoptOpenJDK's OpenJDK version 11.0.8.10 with JVM Openj9.

While the above compiles, I ran across documentation that suggests that it is the wrong `classpath` file. I'm not using Eclipse, but the following Eclipse page in the CPLEX documentation says that a Windows environment should use a *.dll file rather than a *.jar file:

CPLEX -> Getting Started with CPLEX

-> Setting up CPLEX

-> Setting up Eclipse for the Java API of CPLEX

The most promising-looking candidate from my search of the CPLEX installation directory is:

'c:/Program Files/IBM/ILOG/CPLEX_Studio129/cplex/bin/x64_win64/cplex1290.dll'

However, if I use this instead of the *.jar file, I a tsunami of errors pertaining to nonexistence of classes. In fact, I get the same errors if I specify an arbitrary non-existent file, so the *.dll file is obviously "not working".

Why would a *.jar file work on Windows, but a *.dll file not? I'm uneasy forging ahead as if all is fine when it clearly contradicts what is in the documentation.

This one will be for the Java newbies, as I'm sure that it is well-known: The *.jar file is for the -classpath argument in both `java` and `javac` commands, while the *.dll file is the "native library" folder path for the -Djava.library.path argument of `javac`. Multiple paths are separated by semicolons.

And for added context, "native" means a library containing functionality that is native to the host machine on which the JVM is executing, not native the JDK. Usage of native libraries represent non-portable dependencies on the specific machine.