how to implement method which can return different object at different time

[Mohit with Josh Mehta]

Hi

In our project I have situation where one method takes some parameters,
based on parameters(list of x kind of objects) in loop method calls database for each x object and validate details
if validation for all objects are thru method should return list of y objects,
if validation fails for one of the x object it should return validation error object( project specific object to details issue to end-user)

so here by same method in one situation we want to return list whereas in another condition we want to return single Validation object.

Important point to note here is there no common super class between List and validation object except "Object" class , which I don't should be good to return as generic return object.

please suggest how should I design method in this situation?

Mohit

[Pat Farrell]

Are you sure you don't want to throw an Exception, which can return error messages, etc.?

[Kaustav Ganguly]

I agree with Pat, its better to throw exception in case of an error and handle it in the calling method.

[Maneesh Godbole]

Mohit with Josh Mehta wrote:

Please check your private messages for an important administrative matter

[maitrayi vasishtha]

If you are not sure of the method return type, you return generic Object in a method signature

In calling routine , find out the type of the returned object using getClass().getName() and then type cast it and then use it.

e.g.

class Test1{
public Object method1(int a){
     Object ob = null;
      if(...)
          ob = new A();
      else
         ob = new B();

     return ob;
}
}

in calling routine

Test1 t = new Test1();
      Object o =  t.m1(5);
      if(o.getClass().getName().equals("A"))
      {
              A a =  (A) o;
             //use a
      }
      else
       {
             B b = (B) o;
            //use b;

       } 

[Rob Spoor]

1) Use code tags

2) Don't use that construct for checking the class. If you ever decide to use this (which I wouldn't in this case, I'd go for the exception) use the instanceof operator instead:

// if(o.getClass().getName().equals("A"))
if (o instanceof A)

[maitrayi vasishtha]

Thanks Rob for suggesting use of codetags.

As I am new to this forum , it was not known to me. Sorry.

I agree with you that instead of using getClass().getName() better use instanceof operator.

Thanks

[Maneesh Godbole]

Maitrayi
I have edited your post to incorporate the tags for you.
In future you can use the to edit your posts.

You might want to check out http://faq.javaranch.com/java/HowToAskQuestionsOnJavaRanch and http://faq.javaranch.com/java/HowToAnswerQuestionsOnJavaRanch for tips on how to get the most out of the Ranch.

[maitrayi vasishtha]

Thanks Maneesh.

[salvin francis]

to implement method which can return different object at different time

I believe its a bad design pattern to do that