Exam Lab Question

[Duran Harris]

Question 20 from Devakas Exam Lab(Practice Exam 3 I think)

import java.io.*;
interface Buildable
{
	public void BuildNow() throws IOException,ClassNotFoundException;


}
abstract class UDI implements Buildable
{

 public abstract void buildNow()throws IllegalThreadStateException,ClassNotFoundException;

}

public class Nonc extends UDI
{

//Insert Code Here

}

This is really confusing me because I can't figure out which method to implement..
Any tips?

[Ruben Soto]

A concrete class can't have abstract methods, so it must implement all the abstract methods from its ancestors. You need to implement both BuildNow() and buildNow() (I'm guessing these are two different methods and not a typo.)

[Punit Singh]

It's a typo Ruben.

You need to implement only UDI method.

   
abstract class UDI implements Buildable 
{ 

public abstract void buildNow()throws IllegalThreadStateException,ClassNotFoundException; 

} 

public class Nonc extends UDI 
{ 

public void buildNow()throws IllegalThreadStateException,ClassNotFoundException{} 

//or	public void buildNow() throws ClassNotFoundException {}
//or 	public void buildNow() {}
//or many more like public void buildNow() thrown any runtime exception{}
}  

As Nonc is extend UDI, and UDI is already implemented Buildable buildNow() as Abstract, you have to satisfy only UDI's buildNow() method.

[Jesper de Jong]

Please use code tags when you post source code.

[Duran Harris]

Yes it was a typo.

But UDI has not implemented the interfaces methods..It has declared the method as abstract.So it is up to Nonc to implement UDI's buildNow method as well as Buildables buildNow method.But how can it do this?

[Ruben Soto]

There is only one method. The abstract class is "overriding" the interface method.

[Punit Singh]

Duran, Nonc cannot see now Buildable method, as it has been declared as abstract by its implementor class UDI.

[Duran Harris]

Is IllegalThreadStateException a runtime exception?

[Punit Singh]

Yes Duran, and your exam is on Friday, just open K&B 6 book, go to chapter 5 page 382 Table 5-2, here all runtime exceptions are given, also which are thrown by JVM and which are by Programmer, mug up this, make a small diary or note, write down this as a small quiz, it will help you in last hours before your exam.

Make all such notes, at least to see one time before your exam.

[Duran Harris]

Oh that explains it then...