JAVA questions I encountered during an interview

Blase · #1 28-Mar-2008, 20:41

Hi,

These are questions I encountered during an interview. With my introductory background, I had no idea what got into them. Could someone tell me where I should start my search for the answers? Appreciate your hints.

Write a function in that integrates a globally given function f?
What is the danger of using public unsigned integers within a class?
In a diamond-shaped inheritance hierarchy, how to ensure that only 1 copy of parent is created?

Thanks in advance

TurboPT · #2 29-Mar-2008, 19:58

Quote:

Originally Posted by Blase

Write a function in that integrates a globally given function f?

Not sure what you're asking here. Just create a function to call another public function?

Quote:

Originally Posted by Blase

What is the danger of using public unsigned integers within a class?

Two things:
1. Java doesn't know 'unsigned ints', which is discussed here.
2. Web services and XSD can be problematic with Java:

Quote:

Some features of XSD schema cannot be represented well in
some current platforms. One example is the unsigned inte-
ger types in XSD. Although .NET provides unsigned types,
Java does not. Therefore using unsigned integers types
within interoperable Web services is not recommended

That snippet was found here. (search the PDF to find it)

Quote:

Originally Posted by Blase

In a diamond-shaped inheritance hierarchy, how to ensure that only 1 copy of parent is created?

I'm still pondering this one, but I think it has to do with 'final' classing, but I'm not 100% certain.

JustinFox · #3 25-Apr-2008, 13:36

In java programming (or for any languange for that matter), a "diamond-style hierarchy" is a very bad programming technique.

For one, you can't extend from two classes anyways. if you have multiple class that use similar methods, just use an interface.

Diamond-style hierarchy is known as the "diamond of death".

Justin Fox

JustinFox · #4 28-Apr-2008, 11:44

but if you wanted to know how many copies of a class is made, or restrict them, you would just have a static int and just increment that int on each init() of the object.

JAVA Code:


public class A 
{

   static int copies = 0;

   public static getCopies(){
   return copies;
   }

   public A{
   copies += 1;
   }

   public static void main (String[]args)
   {

      int i = 0;

      while ( i < 9)
      {  

       if(A.getCopies > 2)
       System.out.println("Out of memory");
       else{
       A my1A = new A();
       System.out.println("Memory Allocated");

       i ++;
       }

       }

   }

}

Justin Fox

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JAVA questions I encountered during an interview

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