Can an observable class be constructed as a singleton?

Question

I\'m making a program in Java with the Observer pattern (with the help of the Java API). If some of the observables had more than one instance, the program could crash. Should I

Answer 1

Should I implement them as singleton? Is it recommended?

Of course you can do this. Whether it is a good idea depends on the actual context.

• Are these things conceptually singleton, or is this just a hack to try to make bugs disappear? (Or to put it another way, is the real problem that your application design is wrong ...)

• Singletons do have issues with respect to unit testing. This is not a show stopper, but it is one of the reasons that people tend to avoid them.