I know that this
refers to a current object. But I do not know when I really need to use it. For example, will be there any difference if I use x
instead of this.x
in some of the methods? May be x
will refer to a variable which is local for the considered method? I mean variable which is seen only in this method.
What about this.method()
? Can I use it? Should I use it. If I just use method()
, will it not be, by default, applied to the current object?
Best Answer
The
this
keyword is primarily used in three situations. The first and most common is in setter methods to disambiguate variable references. The second is when there is a need to pass the current class instance as an argument to a method of another object. The third is as a way to call alternate constructors from within a constructor.Case 1: Using
this
to disambiguate variable references. In Java setter methods, we commonly pass in an argument with the same name as the private member variable we are attempting to set. We then assign the argumentx
tothis.x
. This makes it clear that you are assigning the value of the parameter "name" to the instance variable "name".Case 2: Using
this
as an argument passed to another object.Case 3: Using
this
to call alternate constructors. In the comments, trinithis correctly pointed out another common use ofthis
. When you have multiple constructors for a single class, you can usethis(arg0, arg1, ...)
to call another constructor of your choosing, provided you do so in the first line of your constructor.I have also seen
this
used to emphasize the fact that an instance variable is being referenced (sans the need for disambiguation), but that is a rare case in my opinion.