Why use this keyword when we can do same without using it?

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I am confused about why do we use this keyword when we can do same by directly referring using the attribute name. Below is example where I used name and this.name. What is the point in using this keyword if same can be achieved other way.

Java

class Myclass
{
    String name;
    public Myclass(String n1)// n1 represents name
    {
        name=n1;
    }

    public Myclass(String firstname,String lastname)
    {
        this.name = firstname + " " + lastname;
    }
}

Posted 25-Jul-13 13:48pm

Infinity Signal

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4 solutions

Solution 4

First of all, so far, the only correct solution is the Solution 1; you should accept Solution 1 formally, and probably should reject Solution 2: readability is important, but resolution of the names is critically important and the case where the lack of "this" would case compilation error is overlooked in Solution 2.

Now, I think you also should understand what "this" actually is. It's is not so trivial as it may seem. Please see my past answer:
C# windows base this key word related and its uses in the application[^].

This is related to instance methods, so please also see:
What makes static methods accessible?[^],
Catch 22 - Pointers to interface objects die when function using them is made static.[^].

(Please don't get confused with some C# and C++ code samples. They explain some first principles which are equally applied to Java and other OPP languages.)

Good luck,

—SA

Posted 25-Jul-13 15:32pm

Sergey Alexandrovich Kryukov

Updated 25-Jul-13 15:40pm

v3

Comments

Ron Beyer 25-Jul-13 21:38pm

+5'd, although I think you transposed the "accept solution 2 and reject solution 1" :)

Sergey Alexandrovich Kryukov 25-Jul-13 21:39pm

Thank you, Ron.
Solution 1.. 2...
OOPS! Thank you for the note, I'll fix it. :-)
—SA

Solution 3

I don't know why anyone else would, but I do because I like to see which items are instance items and which aren't (static, local, etc.) -- but as presented provides little actual benefit.

Posted 25-Jul-13 14:13pm

PIEBALDconsult

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Ron Beyer · Accepted Answer · 2013-07-25T14:05:00

Its not a good example of the use of the "this" keyword. Typically you wouldn't do what you wrote, at least not in clean code.

"this" is used to pass the instance of the class to other functions. You can use the "this" keyword to reference the current instance of the class or pass to other subroutines, but you typically wouldn't use the "this" keyword to access data in the class you are working in. Its not a violation of the keyword, but just doesn't add any value.

[Edit]

I'm not sure if this is valid in Java, but in c# we can also use it in the following way:

Java

class Myclass
{
    String firstname;
    public Myclass(String n1)// n1 represents name
    {
        firstname=n1;
    }
 
    public Myclass(String firstname,String lastname)
    {
        this.firstname = firstname + " " + lastname;
    }
}

To differentiate between the parameter and the class member.

[/Edit]

Steve44 · Accepted Answer · 2013-07-25T14:10:00

As you stated, this is not needed and using the member name without this give the same result. So from the technical standpoint it is not necessary to use this.

However it can be used to make it clear in the code that you are referring to a member variable of an instance of the class and not a (static) class variable. This improves the readability of your code if you follow this convention across your project.