"this" and .width

Question

I have two questions. I'm trying to figure out animations, and in most examples I see, I find that "this" and .width and .height are normally used. For example:
public void init()
     int imageWidth = this.size().width;     // get width
     int imageHeight = this.size().height;     // get height
What is "this" referring to? I was under the impression that "this" was normally used to specify hidden instance variables. How is the program instantiating imageWidth, using the "this" keyword if imageWidth has no value yet?
My second question is where are the .width and .height coming from? And why should I use them as opposed to getWidth and getHeight, which are listed as inherited methods under JApplet, and also under Dimension. Thx.

Answer 1

"this" refers to the same object where it is used. Take a look at the following example:public class A
     private int i;
     public A(int i)
          this.i = i;
     public set()
          int i = 5;
          this.i = i;
}In the constructor, how can you tell if you are referencing the constructor
parameter i or the instance variable i? Using the this operator.
Whenever you have a local variable or a local parameter, you must use the this
operator to reference the instance variable.
size() must be a method which returns an object, lets say SizeObject, with two public fields: width and heigth, like this:public class SizeObject
     public int width;
     public int heigth;
     public SizeObject(public int width,int heigth)
          this.width = width;
          this.heigth = heigth;
}Maybe the getWidth() and getHeigth() methods do the same thing as described by you in the init() method.