BIG T's

Question 1

What’s Abstraction

Answer 1

The process of determining the set of data and methods that a class will have

Question 2

What are two main parts of an object?

Answer 2

It’s properties and methods

Question 3

What’s a class and object?

Answer 3

A class provides instructions for building an object.

The object is what gets built when the constructor method of the class file is called

Question 4

What is Polymorphism?

Answer 4

You can have several methods with the same name defined in different classes of a class hierarchy.
This is called method overriding

Question 5

What is an object?

Answer 5

A particular instance of a class

Question 6

How is a constructor method different?

Answer 6

• Always the same as the class name

- No return type specified

Question 7

What does static mean?

Answer 7

• Means we don’t have to instantiate an object of the class to use the method

Question 8

A static variable is a class variable. What does this mean

Answer 8

• Means it is visible to every method in the class
• Just one copy of class variable in memory
• If changed, all the objects will change

Question 9

How is an abstract method different?

Answer 9

• There is no body code in an abstract method

Question 10

What’s the difference between method overloading and overriding?

Answer 10

• Overloading: Same method name different parameters. Must be defined in the same class
• Overriding: Same method name and signature. Must be used in seperate instances in the sub classes from a class heirarachy

Question 11

Can an abstract method be in a non abstract class

Answer 11

NO

Question 12

Can an interface hold data values

Answer 12

Yes, But by default the values will be constants set as Public, Static and final
- Interfaces can only hold abstract methods

Question 13

What changed in JDK 1.8?

Answer 13

• Interfaces can now hold methods with default implementation and they can be declared static

Question 14

What are the two main uses of interfaces?

Answer 14

• Write an abstract method and have a large number of classes implement them
• Multiple Inheritance Stimulation

Question 15

Can you instantiate and object from the interface?

Answer 15

NO, but the JVM can

Question 16

What’s an abstract class and when is it created?

Answer 16

• Whenever we create objects of the sub class, JVM will internally create an object of the abstract super class

Question 17

What must be done for Polymorphism to work?

Answer 17

The objects of the subclasses have to be created and referenced by a variable of the superclass