Question

Does the this prefix for accessing member variables exist in Java?

Here is my HelloWorld code:

public class HelloWorld {

    public static int x = 0;

    public static void main(String[] args) {

        HelloWorld.x = 45;

        System.out.println(HelloWorld.x);
    }
}

The above code works with/without the class name prefixing the variable x. However, if i try: this.x = 45; or this->x = 45; I receive an error:

non-static variable this cannot be referenced from a static context

I understand member variables can be accessed without the HelloWorld (class name) prefix, like I have done. But, I want to know if the this prefix exists in Java, how do I use it?

EDIT:

Also, could you provide an example where this is appropriate?

duffymo & byte – I greatly appreciate your help. Thanks.

Answer 1

You’re attempting to use ‘this’ to refer to a static, not an instance variable. ‘this’ is only used to refer to the instance variables of an instantiated object of this class. You cannot use ‘this’ to refer to static variables on a class.

When you use ‘this’ you are saying “I want to refer to the variables of this particular instantiation of this class”. A static on the other hand is always going to be the same variable for the class, irrespective of instantiation.

In addition the correct syntax for referring to an instance variable is by the dot operator:

this.x = 42; //correct
this->x = 42; //will not compile as its not valid Java

So essentially what you’re after is something like the following:

public class Foo {

    private int x;

    public void setX(int x) {
        this.x = x;
    }

    public int getX() {
        return this.x;
    }
}

public class HelloWorld {

    public static void main(String[] args)
    {
        Foo foo = new Foo();
        foo.setX(45);

        System.out.println(foo.getX());
    }

}