Inheritance and Polymorphism

Question 1

Inheritance relationship explained.

Answer 1

“Is-a”. I.e. Tiger is a mammal is an animal.

Question 2

What is low cohesion?

Answer 2

One class does too many things.

Ideally, each class does one thing well.

Question 3

What is high coupling?

Answer 3

When classes make lots of calls between each other.

Ideally, the number of calls between classes is limited.

Question 4

Inheritance java syntax.

Answer 4

pubic class Parent {
// implementation
}

public class Child extends Parent {
// implementation
}

Question 5

What does every class in java inherit from?

Answer 5

Either directly or indirectly, they all inherit form Object.

Question 6

How to check if an object is an instance of a specified type?

Answer 6

Use instanceof
I.e. anObject instanceof Type

Question 7

How to redefine a method in a subclass?

Answer 7

use @Override before the method. (may be optional in Java, but apparently used for javadocs).