What does "this" do in Java?

Question

k, I am going through few Game Development Tutorials of Java, and I have to work with Threads and there is a "this" thing Thread thread = new Thread(this); that I am unable to understand, I am implementing my Class by "Runnable". What I think about it, is that "this" refers to Runnable to seek for the Run Method that I have defined in MY Class. And If I don't do this, It won't be looking for Run() Method here in my Class. Don't really know If M-Effed, but please correct me If I am wrong....

Please, please, please find a book on basic object-oriented programming and read it. — Hot Licks, Feb 16 '14 at 22:30
But I really don't understand. Here there are a lot of people who start difficult real application without any java(or other PL) knowledge... — Ashot Karakhanyan, Feb 16 '14 at 22:45

score 2 · Accepted Answer · edited May 23 '17 at 12:07

this is a pseudo-variable that points to the current instance, to the object itself where the method is being executed. So for example:

public class Person {
    private String name;
    public void setName(pName) {
        this.name = pName
    }
}

Person p = new Person();
p.setName("Peter");

In the above code, we're assigning the new name "Peter"to this person p, the current instance of the class Person. In other words, from the point of view of p, this is pointing to p.

score 0 · Answer 2 · answered Feb 16 '14 at 22:37

@Óscar López explains what this means.

If your code contains this:

    Thread thread = new Thread(this);

then this refers to an instance of the class that contains that statement. Furthermore, it is the instance that is running the code. Furthermore, the API spec of that Thread constructors means that this needs to be an instance of a class that implements Runnable.

In short, your class needs to be declared as implements Runnable, and it needs to have a method with this signature:

    public void run()

What does "this" do in Java?

2 Answers2