Method argument of different types

Question

I want to write method that would accept parameter of types a.A or b.B. Currently it's implemented:

import a.A;
import b.B;

...
public void doSth(A arg) {
      SpecificClass.specificMethod(arg);
}

public void doSth(B arg) {
      SpecificClass.specificMethod(arg);
}

I want to have one generic method "doSth" that use wildcards and accepts only a.A or b.B. Important information a.A and b.B aren't subtypes of each other. The only common type is java.lang.Object.

Any help?

Answer 1

Assuming you could do that, if A and B have no common superclass, you won't be able to call any methods on the arguments but Object's methods.

So I think the only 2 reasonable solutions are:

• have two methods, one for A and one for B (your current setup)
• have one method that takes an Object as a parameter, check that the argument is an instanceof A or B, and if not throw an IllegalArgumentException

Answer 2

You may wrap both A and B extending a common interface, just like:

interface CommonWrapper {
  public void doSth();
}

public class AWrapper implements CommonWrapper {
  private A wrapped;
  public AWrapper(A a) {
    this.wrapped = a;
  }

  public void doSth() {
    // implement the actual logic using a
  }
}

public class BWrapper implements CommonWrapper {
  private B wrapped;
  public BWrapper(B b) {
    this.wrapped = b;
  }

  public void doSth() {
    // implement the actual logic using b
  }
}

Then modify your method doSth to accept a CommonWrapper object as parameter:

public void doSth(CommonWrapper c) {
  c.doSth();
}

Answer 3

public <T> void doSth(T arg) {
      SpecificClass.specificMethod(arg);
}

will be called :

yourClass.doSth(yourarg);

But it doesn't restrict to anything that can extend object, whats the point everything does.I would suggest having both your classes implement a common interface and then program to that interface.