CODEWITHSUNDEEP
javaandroid
Snowcrash
Snowcrash

Reputation: 86187

Calling instance method in Java

Following this tutorial:

http://developer.android.com/training/notepad/notepad-ex2.html

In Step 2, this method gets called:

registerForContextMenu(getListView());

which is a public method of Activity. Now, I'm a bit of a Java newbie here - I thought if you wanted to call an instance method of a superclass you needed to preface it with this. E.g. 

this.registerForContextMenu(getListView());

Is it just a style thing here? Is there any difference between 

this.registerForContextMenu

and simply 

registerForContextMenu

Upvotes: 1

Views: 1036

Answers (4)

navyad
navyad

Reputation: 3860

To call a method of superclass either you need object of superclss or keyword super . eg. 

superObject.superclassMethod();
    super.superclassMethod();

this is a reference of the current object. this can be used to call method of a class in which it is used. this can never be used to call a superclass method.

As for 

this.registerForContextMenu()

and 

registerForContextMenu()

no such difference. you can use either of them.

Upvotes: 1

Marcin Orlowski
Marcin Orlowski

Reputation: 75629

you do not have to use this. If you ommit it it is assumed you called method in this scope. One particular example when this may help could be i.e.:

Boolean someVar;
public function setMe( Boolean someVar ) {
  this.someVar = someVar;
}

In this case, w/o this you would get the error.

Upvotes: 1

Dan D.
Dan D.

Reputation: 32391

Both ways are correct for calling a method on the current (this) instance of the class. Non private methods are inherited from super classes, so you can use the same syntax to call such methods.

Upvotes: 0

Keppil
Keppil

Reputation: 46219

No, there is no difference.

You don't have to use this., but it is often done anyway to make the code clearer.

For one thing, it makes it easy to tell if a method is static or not if you use the convention of calling instance methods like this: 

this.registerForContextMenu() 

and static methods like this:

ClassName.staticRegisterForContextMenu()

Upvotes: 2

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