@Override annotation, I’m looking at you
Being out of touch with Java coding and moving between Java 5 and 6 can be a great way to assume yourself. Couple of days back I stumbled upon a fairly well know Java 5 feature, @Override annotation. Annotations were introduced in Java 5. According to the JavaDoc
public @interface OverrideIndicates that a method declaration is intended to override a method declaration in a superclass. If a method is annotated with this annotation type but does not override a superclass method, compilers are required to generate an error message.
One would read this and think the following code should work perfectly fine:
1 2 3 | interface I { void m1(); } |
1 | class C implements I { |
1 2 3 4 | @Override public void m1() { } } |
But guess what? In Java 5, the compiler gives the following error: “The method m1() of type C must override a superclass method”
The same exact code works perfectly fine on Java 6. You go back and read the Javadocs again and you can’t seem to find a fault. But it turns out that in Java 5, @Override annotation only applied to methods overridden from a superclass and not from Interfaces. (So if you implement a method from an Interface, @Override annotation cannot be applied in Java 5).
This was apparently a bug in Java 5, which was fixed in Java 6. Here is the bug report : http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6399361
This is great, but there is no mention on public JDK 6 JavaDocs nor in the release notes.
Eclipse IDE 3.3.1.1 recognizes the new feature and add the @Override annotation auto-magically every time I override a method or implement an interface method. Pretty cool! Unfortunately for all you Intelij fans, there is an open bug still waiting to be fixed.
