8 questions I dont understand while studying for SCJP

[shankhas]

Hi all,
I want to give my SCJP exam sometime this month. I was reading A Concise and Comprehensive Study Guide for SCJP by Dr. Paul S Sanghera. I would like to ask the learned members of this forum you a few queries that I have. I shall be grateful if you would kindly find time to reply me with your valuable suggestions

1. I know that: If a class is declared final, it means the class cannot be extended, and a final method cannot be overridden. If the element declared final is a variable, that means the value of the variable is constant, and cannot be changed.

My question is: If a final variable is inherited in another class, can it be accessed? And can its value be changed?

2. My question is: Could you please give an example of method call conversion of object reference types?

3. My question: Is it possible to inherit the main() method?

4. My question is: What are anonymous inner classes? Where are they used practically? How are they defined? What is their scope? Can they access variables of the outer class? If so how?

5. Can inner classes be defined inside a method? What is their scope? Can they access the variables within the method? Can they access the variables of the outer class?

6. Are all methods defined in java.lang.Math static?

7. What are factory methods?

8. My question: Can interfaces have classes?


Thanks for your help!
waiting for your quick reply!

[Fubarable]

Most of this can be easily looked up. I counter your questions with a couple of my own: Have you looked these up and wouldn't it be wise for you to present your answers and justifications here first before asking for other's advice?

This would serve two purposes. It would demonstrate that you've done your own work first, and will give a starting point for answers to your questions.

Good luck.

[Eranga]

Yes, most of the questions are not directly related with theories of Java. So you can simple write some code and see what happened. In that way you can learn a lot. First make a try.

[coyne20]

My response in red below:

Hi all,
I want to give my SCJP exam sometime this month. I was reading A Concise and Comprehensive Study Guide for SCJP by Dr. Paul S Sanghera. I would like to ask the learned members of this forum you a few queries that I have. I shall be grateful if you would kindly find time to reply me with your valuable suggestions

1. I know that: If a class is declared final, it means the class cannot be extended, and a final method cannot be overridden. If the element declared final is a variable, that means the value of the variable is constant, and cannot be changed.

My question is: If a final variable is inherited in another class, can it be accessed? And can its value be changed?

Yes it is accesible but you can not modify it whatsoever.

2. My question is: Could you please give an example of method call conversion of object reference types?

What exactly do you mean by this?

3. My question: Is it possible to inherit the main() method?

Yes you can but why would you want too?
As main is defined as static. You can not override static.

4. My question is: What are anonymous inner classes? Where are they used practically? How are they defined? What is their scope? Can they access variables of the outer class? If so how?

5. Can inner classes be defined inside a method? What is their scope? Can they access the variables within the method? Can they access the variables of the outer class?


public int someMethod()
{
class Test // class declaration
{
private int i = 5;
public int getI()
{
return i;
}
}
Test t = new Test(); // invoke an instance
t.getI();
}

And yes they can access outer class members using the reference
<OUTERCLASS>.this.<method/variable>;




6. Are all methods defined in java.lang.Math static?

Yes they are. Classic example is Math.PI.

7. What are factory methods?
Beats me what are they?

8. My question: Can interfaces have classes?
Hell no!

Thanks for your help!
waiting for your quick reply!

[Eranga]

2. My question is: Could you please give an example of method call conversion of object reference types?

You mean that how to invoke (call) a method on a different class by using an object?

[r035198x]

8. My question: Can interfaces have classes?
Hell no!

interface Hell {
	class No {
		public static void main(String[] args) {
			System.out.println("Hell, Yes!");
		}
	}
}