annotations error

[medhaj hambi]

Hi ,

I am using a small error when I am using override annotations. I fail to understand why. Can any body pl help me out ?

My code looks something like this :


//@Override
public ArrayList<String> call() {
/* to guard against multiple invocations, synchronize on uniqueId */
String uniqueId = institutionId.intern();
synchronized (uniqueId) {
ArrayList<String> l = opacBaseList.get(uniqueId);
if (l == null) {
l = findOpacBase(uniqueId);
if (l.size() > 0) {
opacBaseList.put(uniqueId, l);
if (Config.verbose) {
Utils.printLog("OCLC: %s baseopacurl(s): %s", uniqueId, l);
}
}
}
return l;
}




When I comment out the annotation I am able to compile. If I remove the comment for the line ----> @override , it gives me the following error:


The method call() of type new Callable<ArrayList><String>>(){}
must override a superclass method


Am not able to figure out what could be the problem.

[Sean Clark]

Hey,

Basically this is used to help identify methods which override/implement methods from super classes.

An example would be the toString() method, typically most java classes will override this and you can use the @Override annotation to show.

I think it is correct to say that this annotation is optional and code will compile fine without, more of a visual aid.

The reason that you are getting this compilation error is because you don't have and method call() in any super class/interface.

Sean

[Christophe Verré]

This is also clearly mentioned in the java.lang.Override API.

[Rob Spoor]

And please UseCodeTags next time.

[Jesper de Jong]

What class is your call() method in? What is the superclass of that class or what interfaces does it implement? Does a class higher up in the class hierarchy or one of the interfaces also have a call() method or not? Which Java version are you using?

Note that in Java 5, the @Override annotation could only be used with classes - not with interfaces. So if you implement a method from an interface, then in Java 5 you could not use the @Override annotation - it would give you a compiler error.

In Java 6 this was changed so that you can also use @Override for methods implemented from interfaces.

interface ExampleInterface {
    void method();
}

class ExampleClass implements ExampleInterface {
    @Override    // Fails in Java 5, but works in Java 6
    public void method() {
        System.out.println("Hello World");
    }
}

[medhaj hambi]

Hi,
Thanks for the reply. I am using Java 6 Version. Also, this is how my class definition starts ...

new Callable<ArrayList><String>>() {

// the above given method goes here...


}

I tried changing the method signature to Public ArrayList<String> call() throws Exception but that was of no use. Also , I am using Java 6 , so that shouldnt be the issue I guess. I have seen people implementing this sort of notation with callable class but I fail to understand why it doesnt compile.

[John de Michele]

Medhaj:

Shouldn't that signature be like this?:

public class SomeNewClass implements Callable<ArrayList<String>> {
...
}

John.

[medhaj hambi]

Well..I am decalring a class inside a method. I dont remember the terminology for that but it goes something like...

mymethod( new Callable<Arralist<String>>()
{
// the code above.

}
);

There is nothing wrong with the syntax as far as I know.