Is it wise to have a static method be responsible for creating the object of the class it resides in?

Question

I came across this type of code recently:

final class OnlyMe {
 private int a;
 private int b;

 //setter and getters for a and b.

 private OnlyMe(){}

 public static OnlyMe getOnlyMeObj(int c) {
 // use c value to connect to database
 // to populate a and b     
 if(rs.next()) {
  OnlyMe onlyMe = new OnlyMe();
  onlyMe.a = rs.getInt(1);
  onlyMe.b = rs.getInt(2);

  return onlyMe;
 } 

 // return null for everything else.
 // assume the code is under try-catch block.
 return null;
}

So, its seems like the 'getOnlyMeObj(int)' could be extracted out to another class. But it seems like the developer wanted this class to be only created by that method depending upon the input to that method.

What would be a reason for that?

Is this some type of pattern or anti-pattern or no pattern?

Is there a better solution?

It is a static factory method. The private constructor forces you to rely on that method so you get instances that already have all values set (which come from a database). — f1sh, Jan 17 '19 at 15:48
Thanks for the link. I also read the answer from [this link](https://stackoverflow.com/questions/929021/what-are-static-factory-methods). But is there a better solution for this scenario? — Harke, Jan 17 '19 at 15:57

score 1 · Accepted Answer · answered Jan 17 '19 at 16:10

1

This is a static factory pattern. The idea is to create instances of an object via a static (class-level) method and return it. There are several possible uses of this pattern:

there might be several possible constructors and you might want to avoid letting the code which needs a new instance choose the constructor
if there are multiple factories, confusion can be reduced by their naming
this way you have the option of validating some parameters and instantiate only if they are valid
you can have factories, which might return subclasses, not necessarily the best thing to do, but still an option

see: see: https://www.youtube.com/watch?v=sOpbAOX5nJs

answered Jan 17 '19 at 16:10

Lajos Arpad

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Thanks, this answers my question. I also found an example to your second point [here](https://stackify.com/static-factory-methods/). – Harke Jan 17 '19 at 16:23
@Harke it's great that your problem has been solved. The example is also good. – Lajos Arpad Jan 17 '19 at 16:34
is static factory pattern the same as static factory method? – Harke Jan 17 '19 at 18:46
@Harke the factory method is the actual method, the pattern is the strategy to use such methods. – Lajos Arpad Jan 17 '19 at 20:20

score -2 · Answer 2 · answered Jan 17 '19 at 15:57

This looks like Factory method pattern, but implemented not so good. You can also use Abstract factory pattern. More context is required to get what pattern will be the best choice. You also can check if there is a similar kind of problem in your project and how this problem is solved there.

Is it wise to have a static method be responsible for creating the object of the class it resides in?

2 Answers2