2.4: Hello World!
Intro: Welcome to coding! Iım going to give you some key vocab
and ideas each day.
Classes: Program components; defines or describes a list of data
resources
Instance
Variables: Data resources
Methods: Rules of behavior
Information
Hiding: Access to services but not to
resources
Example: Object A can use Object B but doesnıt
know Object Bıs resources
Inheritance: Base class (root class) can use methods and instance
variables defined in subclasses
Polymorphism: Different objects can understand same message but their
responses may be different depending upon the class to which it belongs
Object-Oriented
Programming sends
messages to objects.
Generic Message:
<object name>.<message>(<parameters>)
Note: The period (.) between the objectıs
name and messageıs name is called a method selector operator.
Example:
System.out.println(³Hello
World.²);
System.out
= name of object
println =
name of message
³Hello
World² = parameter (text)
; = end of
a line of code, completes instruction