How do I prevent implicit Java compilation when the class exists in the classpath?

Question

Let's say that I have two classes (Bob and Tom) such that Bob uses Tom, but Tom does not require Bob. Both of these files are located in the same directory structure.

public class Bob {
  public static void main(String[] args) {
    System.out.println(Tom.MESSAGE);
  }
}

public class Tom {
  public static String MESSAGE = "Hello World";
}

If I attempt to compile Bob in the typical fashion, I can get it to implicitly compile Tom.java as well since it is recognized as a dependency of Bob.java. That works great.

But now let's say that I want to place Tom in a JAR file. So I build Tom.java and place the results into a JAR file: libTom.jar. I now compile with the classpath pointing at libTom.jar. Unfortunately, the compiler sees the Tom.java file and causes it to be compiled rather than using the class in libTom.jar. Is there a way to get the compiler to skip the implicit construction of Tom.java if the class is found in the classpath?

I recognize that this example is fairly contrived. Rest assured that there is a more complicated, less contrived use-case that surrounds this issue. Thanks.

Answer 1

If there are two classes with the same name and in the same package in the classpath, it is difficult to predict which one will get picked up when java compiles the code. In case the Tom class exists in the source itself, it will surely get picked up.

One way you can avoid it is to put one of the Toms in a different package. Another way is if you can move your current Tom to a separate project. I understand either of these might not be practical for you. If it is really necessary, you could experiment with writing your own ClassLoader. See this question for reference: Jar hell: how to use a classloader to replace one jar library version with another at runtime

Answer 2

It appears that this just isn't possible, which is what I feared from the beginning.