OOP core ideas

1. OOP - Object Oriented Programming - An approach to programming that relies on objects and their interactions
   
2. Object - a bundle of data and code
   
1. Encapsulation - Objects encapsulate data and code
   
3. Class
• Properties/attributes
  
• instance variables - not declared static
  
• class variables - declared static
  
• Methods/Behavior
• instance methods - not declared static. Invoked with reference to an object. Object reference provides the context
• class methods - declared static. Can only reference class variables. Invoked with reference to a class. Class name provides the context.
4. Information hiding
• Visibility modifiers
  
• private - limits visibility to the containing class
  
• public - visible everywhere, including within methods defined in other classes.
• public interface vs. private implementation
  
5. Java keywords
1. static - discussed above
   
2. this - mechanism that allows an object to refer to itself