errorprone reports:

java/java/util/Collections.java:3819: warning: [IsInstanceOfClass] The argument to Class#isInstance(Object) should not be a Class

            @SuppressWarnings("unchecked")
            public Object[] toArray() {
                Object[] source = s.toArray();

                /*
                 * Ensure that we don't get an ArrayStoreException even if
                 * s.toArray returns an array of something other than Object
                 */
                Object[] dest = (CheckedEntry.class.isInstance(
                    source.getClass().getComponentType()) ? source :
                                 new Object[source.length]);

although the only consequence of the mistake is an extra copy.