Question

i am developing a Java Api to do things (secret, uhhhh ;).

Is there a way to hide classes, and the internal structure of my API?

What i found until now:

• Using inner classes (ugly way, i do not want to put all in on class file)
• All classes in one package so that i can use the “package”-visibilty (also ugly, i need more packages)

Example:

---
package net.my.app;
//this is the Public Access
class MyPublicClass{
    public void somePublicFunction(){ 
        //access to not visibil classes
    }
}

---
package net.my.app.notvisible:
//this is what i want to hide
class MyNOTPublicClass{
    ...
}
---

Any ideas?
Thank you!

Answer 1

• Use interfaces to define what your
  app does
• Create a main entry point to accesses services, returning interfaces only
• I wouldn’t bother about actually hiding the implementation classes. You can never really hide them in Java, and those who are technically interested might just start your app with a debugger. Just provide no public constructors, for example

Regarding this comment:

Sean, would you elaborate a little
more on your answer? …

One way to implement my second bullet point I mean using a Service Lookup class, e.g.

public class Lookup {
    private static final Foo foo = new FooImpl();
    public static Foo getFoo() { 
        return foo; 
    }
}

Foo is an interface, FooImpl an implementation class (which can be package private if you want to enforce that it can’t be instantiated by clients)