Using this as a parameter for addfocuslistener method

Question

uQty.addFocusListener(this);

I am working an example from Object Oriented Design in java, and am perplexed about the use of this as a parameter for the addFocusListener method. I have done an extensive online search for an explanation, but all I get are more examples with no explanation. Does this refer to the field or the object that the field is part of?

Possible duplicate of [What is the meaning of "this" in Java?](https://stackoverflow.com/questions/3728062/what-is-the-meaning-of-this-in-java) — Joshua Burt, Oct 18 '19 at 14:50
Does this refer to the field or the object that the field is part of, as a field(attribute) is based on an object? — Tom Magaro, Oct 19 '19 at 14:06

score 0 · Answer 1 · answered Oct 19 '19 at 14:30

this refers to the instance of the object that it is used in. So when using uQty.addFocusListener(this), it would be in a class that implements FocusListener.

For instance (For this example I'm going to assume uQty is a JTextField):

public class Foo() implements FocusListener {
    public Foo() {
        JTextField uQty = new JTextField("A TextField");
        uQty.addFocusListener(this);
    }
}

In this example, this refers to the class Foo, and as the class implements FocusListener it can be added to an object as one.

That's what I thought, but the usage seemed a little ambiguous. — Tom Magaro, Oct 21 '19 at 11:15

Using this as a parameter for addfocuslistener method

1 Answers1