What exactly is an instance in Java?

java oop object reference instance
priya picture priya · Feb 26, 2011 · Viewed 263.4k times · Source

What is the difference between an object, instance, and reference? They say that they have to create an instance to their application? What does that mean?

Answer

Mark Byers picture Mark Byers · Feb 26, 2011

An object and an instance are the same thing.

Personally I prefer to use the word "instance" when referring to a specific object of a specific type, for example "an instance of type Foo". But when talking about objects in general I would say "objects" rather than "instances".

A reference either refers to a specific object or else it can be a null reference.

They say that they have to create an instance to their application. What does it mean?

They probably mean you have to write something like this:

Foo foo = new Foo();

If you are unsure what type you should instantiate you should contact the developers of the application and ask for a more complete example.

Related questions

Can we instantiate an abstract class?

During one of my interview, I was asked "If we can instantiate an abstract class?" My reply was "No. we can't". But, interviewer told me "Wrong, we can." I argued a bit on this. Then he told me to try …

Read More
What is the purpose of Serialization in Java?

I have read quite a number of articles on Serialization and how it is so nice and great but none of the arguments were convincing enough. I am wondering if someone can really tell me what is it that we …

Read More
Factory classes

Personally I've never understood the idea of factory classes because it seems a whole lot more useful to just instantiate an Object directly. My question is simple, in what situation is the use of a factory class pattern the best …

Read More