CSIS 110 โ Lecture 29
Reading โ Sections 7.5 and 7.6
Quiz โ Monday, March 28
Last time we discussed class variables, name reuse, and name hiding
Class variables
A class variable is independent of the objects in the class. There is only one instance of a
class variable, regardless of how many objects exist.
Let's look at a class that includes a class variable - Counter.java
The methods reset(), getValue(), and click() should all be pretty familiar to you -
they are instance methods.
Method getHowMany() is a class method - note the keyword static
The variable howMany is a class variable - again, note the keyword static.
howMany gets initialized to 0, and is incremented everytime the Counter constructor is
invoked.
[Draw picture]
Class variable gets created only once โ when you first reference the class.
Instance variables get created for every object โ every object has its own set of instance
variables.
Name Reuse and Hiding
Last time we looked at reusing variable names, and we saw that there were certain
situations where we could declare a variable that hides or shadows another variable of the
same name. In particular, a local variable or a FP can hide an instance or class variable.
Let's look at some examples - see Scope.java
Can I make these definitions:
-define a for loop control variable x in main after local variable x
-define a local variable x in print()
-define an instance variable x in Scope
Can I define a local variable x in print2()?
