Object-Oriented Data-Structures - A Concise and Practical Introduction to Programming Algorithms in Java - page 182

using the keyword this . The example below illustrates the essential difference
between the two ways of programming the Volume functionality.

Program 8.10 Object-oriented method for computing the volume of a 3D
box
class Box
double width , height , depth ;

Box( double w, double h, double d)
this .width=w; this . height=h; this .depth=d;
}

double Volume ()
{ return this .width ∗ this . height ∗ this .depth; }
}

class OOstyle
static double Volume(Box box )
{ return box . width ∗ box. height ∗ box . depth ; }

public static void main( String [ ] s )

Box myBox= new Box(5,2,1);
System . out . println ( "Volume by static method:" +Volume (myBox) ) ;
System . out . println ( "Volume by object method:" +myBox . V o l u m e ( ) )
;

}
}

8.5 Revisiting object-oriented style
data-structures

8.5.1 Object oriented priority queues

The former maxHeap / add / removeTop static functions operating on the array
can thus be translated as equivalent methods acting on the object. A heap
object now declares the array as an object field without that static keyword.
Therefore, we can build several heaps at a time. The prototypes for the heap
methods are as follows: