sometimes .this.method() and sometimes .method()

[blingo james]

Hello
Migrated from C++ to Java,
Working with Eclipse,

Why is it that to use some methods I use

someObject.method()

but sometimes I need to use

someObject.this.method()

?

Many thanks.
[ October 13, 2008: Message edited by: blingo james ]

[Steve Luke]

Originally posted by blingo james:
Hello
Migrated from C++ to Java,
Working with Eclipse,

Why is it that to use some methods I use

someObject.method()

The method belongs to some other Object (instance of a class), and you need to call the method that works on/from that object.

Originally posted by blingo james:
but sometimes I need to use

someObject.this.method()

More appropriately that should be:
SomeType.this.method()

In these cases, code is executing in an instance of an inner class - a class that only lives as part of an instance of the outer class. The inner class has access to the outer class' methods, but you have to tell it that the method you want to call belongs to the outer class' object, and that is what SomeType.this does - basically 'call method() on my reference to the Object of SomeType that I belong to'.

[blingo james]

Thanks for the quick reply.

To understand, I've tried to write something like this:

  
 
class class1
{
 
void x1()
{}


class class2
{
void x2()
{}

class class3
{
}

}
}

assuming I have

  
class1 instance1 = new class1();

Can someone give an example of using 'this' ?

Also - when using 'this' I understand I should use classes and not instances,
but doesn't it mean that the classes should be static?

Many thanks.

[Campbell Ritchie]

Do some searches through the Ranch for use of this. You find 1 2 3.

When you have to say Foo.this.bar(); it means you are inside an inner class, and you are trying to get at an instance member of the object from the outer class. I don't know whether it makes any difference if the inner class is an instance class or a nested class (static).

[Steve Luke]

Originally posted by blingo james:
Also - when using 'this' I understand I should use classes and not instances,
but doesn't it mean that the classes should be static?

Many thanks.

No, it is more of just a name-space identifier. As a matter of fact, the class must NOT be static, because static nested classes don't have an instance of the outer class they belong to - they are static so there is no OuterClass instance, and so no OuterClass.this.

[blingo james]

Thanks, I'll look in the links on hopefully learn this, I get the feeling
it's not 100% the same THIS as C++...

[Satya Maheshwari]

Here is an example using 'this', the way you asked:

public class InnerClassDemo {
    
    class Inner{
        public void innerMethod()
        {
            InnerClassDemo.this.outerMethod();
        }
    }
    
    public void outerMethod()
    {
        System.out.println("This is outer class method!!!");
    }
    
    public static void main(String[] args) {
        InnerClassDemo outer = new InnerClassDemo();
        InnerClassDemo.Inner inner = outer.new Inner();
        inner.innerMethod();
    }
 

[Campbell Ritchie]

Originally posted by blingo james:
. . . not 100% the same THIS as C++...

Java isn't C++. Assume nothing in Java is the same as it is in C/C++.

[blingo james]

Originally posted by Campbell Ritchie:
Java isn't C++. Assume nothing in Java is the same as it is in C/C++.

LOL I'll try to keep it in mind