If you want to "utomatically" set the classpath as needed, you can set the
CLASSPATH variable to a common setting, or not at all when the current
directory is fine.

Then when starting an application, either use the -jar switch with a JAR
file (and set the classpath in the manifest), or use -classpath/-cp
switches to set the classpath (doesn't work with -jar).

Note however, that the standard classes are always in the classpath, and
that the default classpath is the current directory.

You can of course, create a small script that calls the JVM with the
correct classpath if you don't want to type it again and again.