CODEWITHSUNDEEP
java
Naxels
Naxels

Reputation: 1745

How can I dynamically create a new instance of an object in Java?

I have a class called GetInput.java and I have a class called GetNotReleasedInput.java. I extend GetInput in GetNotReleasedInput. In GetInput, I call a private function called addLineToArray() and in that function I define a new class which contains details about the import.

However since I'm creating a generic class(GetInput) for all input files, I cannot say in addLineToArray():

AAData nextData = new AAData();

because I have AA / Not Released, and in this case it should be NotReleased. So how can I dynamically make that new nextData in that function?

Upvotes: 1

Views: 312

Answers (3)

Donal Fellows
Donal Fellows

Reputation: 137557

Either you make a protected method for creating the nextData object so that subclasses can decide how to do the manufacturing, or you have some kind of factory object (configurable at outer object creation time) that you delegate that to. The simplest way of doing the latter is to pass in a Class and call its newInstance() method, but there's a lot more complexity possible; a book on software patterns will go into quite a lot of depth on this.

But if you can just delegate the whole thing to the subclass of GetInput then that is easiest. (You don't provide enough information for me to be able to work out which pattern you should actually use.)

Upvotes: 2

Pontus Gagge
Pontus Gagge

Reputation: 17258

It sounds like you might want a virtual factory method into which you can place your object creation. In addLineToArray(), you then call your virtual createLineObject() instead of new AAData().

However, exactly what way to go depends on a number of factors: does the kind of data created depend on the GetInput class, or is that a separate decision (your GetInput classes may vary on behaviour, whereas the data may vary by format)? Are all data related (e.g. inherits from AAData)?

You should add more details on what you are trying to accomplish.

Upvotes: 1

Aaron Digulla
Aaron Digulla

Reputation: 328556

Java doesn't allow to modify metadata at runtime by default. You can write your own classloader with a asm and modify the bytecode at class loading time but that's probably not what you will want.

Instead, I suggest that all your classes data classes implement Iterable or something like that so you can easily join then and iterate over all lines without knowing the actual type.

Upvotes: 0

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