Gillmer Derge writes:

When you define an inner class, the compiler adds a reference to the outer class object (usually called something like "this$0", use javap to see it). So when you refer to "markerList" what you're really saying is "this$0.markerList," and since "this$0" is an instance variable declared (implicitly) in this class, you're violating that rule. Now, I may be abusing the JLS by using that quote in a way in which Sun never intended, but I don't think it's clearly an abuse.

You might want to try using "Counter.this.markerList" just to see whether that puts you into a different set of compiler rules that don't cause the error message, but I doubt it will help.

The following quote from Section 8.8.5.1 of the Java Language Specification http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html#229267 covers this issue.

An explicit constructor invocation statement in a constructor body may not refer to any instance variables or instance methods declared in this class or any superclass, or use this or super in any expression; otherwise, a compile-time error occurs.

For example, if the first constructor of ColoredPoint in the example above were changed to:

    ColoredPoint(int x, int y) {
      this(x, y, color);
    }

then a compile-time error would occur, because an instance variable cannot be used within a superclass constructor invocation.