Public Object: Don't do this: Share names

Don't do this: Share names

The following program is valid Java, even though the Runnable on line 1 is a completely different symbol than Runnable on line 3:

public class Refrigerator implements Runnable {
  public void run() {
    new Runnable().freeze();
  }

  public class Runnable {
    void freeze() {
      System.out.println("cold and refreshing");
    }
  }

  public static void main(String[] args) {
    new Thread(new Refrigerator()).start();
  }
}

I'm not quite sure if this is shadowing, obscuring or hiding, but it's certainly not good. Writing a compiler must be pretty difficult!

# posted by Jesse Wilson on Friday, April 04, 2008

For what it's worth, this is also a valid (albeit useless) Java program:
class Foo<Bar extends Foo> {
Foo<Foo> Foo = new Foo<Foo>();
Foo() {
Foo.Foo = new Foo<Foo>().Foo.Foo(Foo);
}
<Foo extends Bar> Foo Foo(Bar Foo) {
return (Foo) Foo.Foo(Foo);
}
}

# posted by swankjesse on April 4, 2008 6:21 PM

:D
Jesse: A more useless piece of Java code will be hard to find indeed!
About name scope in a compiler (the Scope class in Javac is quite nice), just imagine what closure is going to do to it!

# posted by Frederic Simon on April 4, 2008 10:26 PM