Field 'sun.nio.ch.Invoker.myGroupAndInvokeCount' uses anonymous class which overrides 'initialValue' method. But vanilla ThreadLocal.initialValue does the same - just returns 'null'.

    private static final ThreadLocal<GroupAndInvokeCount> myGroupAndInvokeCount =
        new ThreadLocal<GroupAndInvokeCount>() {
            @Override protected GroupAndInvokeCount initialValue() {
                return null;
            }
        };

It means we can replace it with plain ThreadLocal constructor.

private static final ThreadLocal<GroupAndInvokeCount> myGroupAndInvokeCount =
            new ThreadLocal<>();