Why is this a warning and not an error? Backwards compatibility. Before the introduction of varargs, you had these methods take a Object[] and code compiled against that should still work the same way after the method has been upgraded to use varargs. The JDK standard library is full of cases like that. For example java.util.Arrays.asList(Object[]) has changed to java.util.Arrays.asList(Object...) in Java5 and all the old code that uses it should still compile and work without modifications.