Chapter 8
Classes, Declaration and Scope
Class vs. Object
public vs. private
public: accessible both inside and outside the class
private: accessible only within the defining class
Examples
•private
•private FramedOval head, leftEye, rightEye, mouth;
•private void resetGame()
Chase.java
•public
•public void move(double dx, double dy)
•public boolean contains(Location pt)
FunnyFace.java
Guidelines
•Instance variables should always be private
•Method should be private if they are helpers
--otherwise public
Variables
•Instance variables
•Parameters
•Local variables
Instance Variables
•Visible throughout class in which declared
•Should be private
•Provided with default value if not initialized
Parameters
•Visible only in constructors and methods in which
declared
•May not be declared public or private
•Associated with actual parameter during method
invocation
•Removed after method execution
Local Variables
•
•
•
•
Visible only in methods in which declared
May not be declared public or private
Removed after method execution
Must be given a value before use
Static
• Shared by all objects of the class
• public static final designates a constant
ex: public static final Math.PI
Color.RED