Question

Here is a more specific example:

public class A {
    public static class B {
             public void f() {
                 synchronized (B.this) {
                     // do something
                 }
             }
     }
}

What does B.this refer to?

Answer 1

It's the active instance ofB. If the class weren't static, you'd also haveA.this` available, to refer to the containing instance of A.

Because the class is static, it should never be necessary to use B.this, as simply this would never be ambiguous.