1) adding the all the logic into main method will make JAVA program as POP.

Object has state and behaviour

Class is a blueprint of object

When designing a class, think about the 1) things the object knows itself are called instance variables 2) things the object does are called

instance variable represents objects state

variable has a type and name and value... int(type) salary(name) = 10(value)

primitive variable is full of bits representing the actual value of the variable,

an object reference variable is full of bits representing a wayto get to the object.

The 3 steps of object declaration, creation and assignment

Dog myDog = new Dog();

An array is always an object, even if the "array is declared to hold primitives". There is no such thing as a primitive array, only an array that holds primitives.

interface vs abstract class

1) Card(Interface) --> Credit Card(Abstract Class)--> VisaCreditCard(Concrete class)

CreditCard card = new CreditCard[10]; ---> How many objects are created...

In a parent child class. Create a instance of Child with parent reference .Call a method on reference, call a variable on reference...parent or child invoked?

In a parent child class. Does creating instance of Child will call parent constructor --->yes

Does the compiler gives no-argument constructor always.? -------------- No.

Life of variables depends on whether it is declared at static or instance or local variable.

Life of static variable ends when a class unloaded.

Life of instance variable ends when a object is garbage collected.

Life of local variables ends outside the stack.

Inner Class scenario--> implement an interface 2 times in a same class and give different behaviour. Ex: Swing Ex: 2 Buttons pressed.