Should we @Override an interface's method implementation?

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Should a method that implements an interface method be annotated with @Override?

The javadoc of the Override annotation says:

Indicates 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.

I don't think that an interface is technically a superclass. Or is it?

Question Elaboration

You should use @Override whenever possible. It prevents simple mistakes from being made. Example:

class C {
    @Override
    public boolean equals(SomeClass obj){
        // code ...
    }
}

This doesn't compile because it doesn't properly override public boolean equals(Object obj).

The same will go for methods that implement an interface (1.6 and above only) or override a Super class's method.

Why use @Override annotation in Java - Coding Best , Why is it important to include @override in front of an overridden method? In java 6 and later versions, you can use @Override for a method implementing an interface. But, I donot think it make sense: override means you hava a method in the super class, and you are implementing it in the sub class. If you are implementing an interface, I think we should use @Implement or something else, but not the @Override.

I believe that javac behaviour has changed - with 1.5 it prohibited the annotation, with 1.6 it doesn't. The annotation provides an extra compile-time check, so if you're using 1.6 I'd go for it.

Can Interface methods overload and override (Java in General forum , anything. It can improve the readability of the source code. @Override indicates a method is being overridden. You don't override methods of an interface - you implement them. @Override is mostly used to spot typos. Lets say you want to create a specific hashCode() method for a class but name it hashcode() instead. If you tag it with @Override, the compiler will complain and you can fix your typo.

You should always annotate methods with @Override if it's available.

In JDK 5 this means overriding methods of superclasses, in JDK 6, and 7 it means overriding methods of superclasses, and implementing methods of interfaces. The reason, as mentioned previously, is it allows the compiler to catch errors where you think you are overriding (or implementing) a method, but are actually defining a new method (different signature).

The equals(Object) vs. equals(YourObject) example is a standard case in point, but the same argument can be made for interface implementations.

I'd imagine the reason it's not mandatory to annotate implementing methods of interfaces is that JDK 5 flagged this as a compile error. If JDK 6 made this annotation mandatory, it would break backwards compatibility.

I am not an Eclipse user, but in other IDEs (IntelliJ), the @Override annotation is only added when implementing interface methods if the project is set as a JDK 6+ project. I would imagine that Eclipse is similar.

However, I would have preferred to see a different annotation for this usage, maybe an @Implements annotation.

Lab 1-4 Flashcards, I was looking at Map and SortedMap documentation from Java 7 and I have realized that SortedMap , which extends Map overrides entrySet() , keySet() and​  In Java 5, you must not add @Override when implementing a method inherited from an interface, in Java 6, you should (or you'll get a compiler warning). @Override asserts that a method is intended to override something, and will cause the compiler to notify you should this not or no longer be the case, for instance because the method you are overriding has been renamed.

I would use it at every opportunity. See When do you use Java's @Override annotation and why?

Importance of @Override annotation in Java?, The @Override annotation was added in JDK 1.5. annotated method must override an existing supertype method, either from an interface, or an abstract base class. You should be in the habit of using @Override whenever you override a  Since Java 1.5, the @Override annotation type has been provided to allow developers to specify that a method declaration is intended to override or implement a method in a supertype (super class or super interface). When a method is marked with the @Override annotation, the compiler will perform a check

JDK 5.0 does not allow you to use @Override annotation if you are implementing method declared in interface (its compilation error), but JDK 6.0 allows it. So may be you can configure your project preference according to your requirement.

Why would an interface override methods of the interface(s) it , Unlike other abstract methods these are the methods can have a default implementation. If you have default method in an interface, it is not  @Override annotation is used when we override a method in sub class. Generally novice developers overlook this feature as it is not mandatory to use this annotation while overriding the method. Generally novice developers overlook this feature as it is not mandatory to use this annotation while overriding the method.

Java Practices->Use @Override liberally, That's why to avoid confusion, we can't have default methods that are overriding Object class methods.” Can you please explain me this again? with some  @Override has an upper-case O. If you use a lower-case o it will be useless. (Or more likely won't compile.) – ajb May 27 '14 at 23:59

Is it mandatory to override the default methods of an interface in Java?, You must explicitly override the supertype methods. Consider the example about computer-controlled cars that can now fly. You have two interfaces ( OperateCar​  The overriding method has the same name, number and type of parameters, and return type as the method that it overrides. An overriding method can also return a subtype of the type returned by the overridden method.

Java 8 Interface Changes - static method, default method, When I implement an interface method, must I specify the override attribute? From the spec, I see: It is an error to define a method without the override attribute if Interface methods can very much be overloaded and overridden. The overriding just must happen in another interface, and is actually only done to specify more constraints in Javadoc. An example is the add method of java.util.Set; this overrides the same method of java.util.Collection.

Comments
  • wow this question could be shorter, but it's the question I needed. Thanks
  • I can't find the replacement for the @Override article (Oracle moved the old Sun blogs recently). Do you know how to find it?
  • We should have an @Implement(s) annotation by now (2015). That will make things clear!
  • by now (2015) should we use @Override with java 8?
  • Note that you cannot add the @Override annotation to a method implementing an interface in Java 5 - it generates an error. It is allowed in Java 6.
  • Um, no, it doesn't. In fact, Eclipse auto-inserts @Override when filling in methods that implement an interface.
  • -1 until the answer includes a mention about the different behaviour from Java 1.5 to 1.6 with regards to implementing an interface method. Just because I've seen it be a confusing aspect for people and it really merits a mention.
  • If eclipse is complaining then upgrade ur jdk to > 1.5 and change the compiler compliance level to 1.6 or 1.7. To do that right click on ur project-> properties-> Java compiler and select one that is higher than 1.5.
  • Can anyone think of an example that actually justifies the answer (implementing interfaces rather than overriding base methods)? A big plus for me is that it aids sets a readers expectations of how and by what a particular method might be used.
  • What is the extra check?
  • @Michael You can notice if any interface has deleted.
  • Calling a super, when not implementing an interface, is not something you always need to or want to do. Sometimes, you're adding functionality -- so you call it. Other times, you're replacing functionality, so you don't call it. An API author should document whether it relies on internal functionality or not and create a documented contract on how the class can be properly extended.