How can we debug method calls that are not part of our own source code, say a call to JButton.setEnabled()? Java provides us with anonymous inner classes, which come in quite handy for this problem.

Q: So what are inner classes good for anyway? A: Inner classes nest within other classes. A normal class is a direct member of a package, a top-level class. Inner classes, which became available with ...

Foo.java:21: warning: [NullAway] Cannot pass parameter of type Foo., as formal parameter has type Callback<@Nullable Integer>, which has mismatched type parameter ...