Error in creating singleton class

Question

Hi all:
I am trying to create a singleton class. The code is the following:
// begin
class EdgeIntersectsException extends Exception{
final static EdgeIntersectsException instance = new
EdgeIntersectsException();
private EdgeIntersectsException(){}
// end
But eclipse gives me error like this:
the field instance cannot be declare static; static field can only be declare in static or top level types.
I don't know why it happens to be like this. Any advice will help. Thank you in advance!

Answer 1

What benefit do you get by making it a singleton?
My program is not suppose to use concurrency, so
, so a singleton design is good, because I am sure
that the instance is going to be
used by one thread at any time, and it also saves
memory space. Being a Singleton has no impact on how many threads can execute code unless every method is synchronized and every member is private. Furthermore, if your program is not using concurrency then this is even more irrelevent because it would only matter if you were using concurrency.
What logic is there that says only one of these
things should exist in your system?
I am not exactly sure here. If I make only one
one instance of this exception, will it be faster to
throw it? Currently, the only good thing
I can think of is that it saves memory. (Since this
kind of exception may be used a lot as the program
runs.)If you can't identify a single meaningful reason to be doing something perhaps you should rethink doing it to begin with.