Java Reference
In-Depth Information
Figure 1.2
An object on the
object bench
Convention
We start names of classes with capital letters (such as Circle) and names of objects
with lowercase letters (such as circle1). This helps to distinguish what we are talking about.
Exercise 1.1
Create another circle. Then create a square.
You have just created your first object! “Circle,” the rectangular icon in Figure 1.1, represents
the class
Circle
;
circle1
is an object created from this class. The area at the bottom of the
screen where the object is shown is called the
object bench.
1.3
Calling methods
Right-click on one of the circle objects (not the class!), and you will see a pop-up menu with
several operations (Figure 1.3). Choose
makeVisible
from the menu—this will draw a rep-
resentation of this circle in a separate window (Figure 1.4).
Figure 1.3
An object's pop-up
menu, listing its
operations
You will notice several other operations in the circle's menu. Try invoking
moveRight
and
moveDown
a few times to move the circle closer to the center of the screen. You may also like
to try
makeInvisible
and
makeVisible
to hide and show the circle.
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