Question

I am a beginner in java and has slowly started to get the feel of this language.

I am having a hard time understanding “this” variable.

For example, which is better.. and why?

  public class Foo{
   int a;
   public Foo(int _a){
   a = _a;
     }
 }

vs

public class Foo{
   int a;
   public Foo(int _a){
   this.a = _a;
     }
 }

Thanks

Answer 1

Personally, I hate those conventions that use the underscore or “m_” to distinguish variables. That’s the stuff that IDEs are meant to make clear.

You use this to clearly delineate variables that belong to the current instance.

Neither of your examples have any advantage. You can prove it to yourself by looking at the byte code that’s produced. If you use javap, you’ll see that the two compile to identical code.

It has more to do with readability for yourself and other programmers in my opinion. And good IDEs, like IntelliJ, use highlighting and color coding to make it even clearer.

The one circumstance where it’s absolutely required is when there’s a name collision between a method parameter and a private member. Then you have to use this to disambiguate which is which for the compiler:

public class Foo {
    private int x;
    public void setX(int x) {
        this.x = x;  // this is required here.
    }
}