$CLASSPATH and -cp with Java

Question

• In this post, using -jar option ignores all the -cp and $CLASSPATH.
• In this post, using -cp option also ignores the $CLASSPATH.

Is there any good reason for them?

Answer 1

It's to avoid clashes in the classpath whenever you distribute your application to run on different environments. In most of the cases you'd like your application to be independent from the platform specific configuration. If the $CLASSPATH contains references to classes with (either unawarely or awarely) the same package and classname, it would get precedence in classloading before the classes which you included in your application's classpath. This may lead to unexpected application behaviour or potential security holes.