Person A reads the declarations and writes down what they do, without mentioning any function names or argument names.

  "This function returns the index of a character in a string."

    int findIndexOf(String s, char c);

Now, at this point, what you have is something functionally the same as Java's String object. Do this for all classes. Call this bundle something like AlterJava. (Or YerksDiddy if you really worry about the name.)

Then someone writes a tool that translates Java into AlterJava. It's an easy thing to put into the compiler chain.

I'm skeptical of these "just hop through this hoop and you aren't breaking the law" ideas when other people make them, so feel free to tell me I'm missing something.

EDIT minor edits