Question

How can I return type Object from a method to an unknown type without causing a type mismatch?

Answer 1

You could use Generics to infer the return type, like this:

public <T> T methodX() {
  return (T) someValue; //Note that you should ensure that this cast succeeds or catch the possible ClassCastException here
}

//call it like this:
String s = methodX();

Note that you need to ensure you can cast to inferred type, so you might want to pass Class<T> as a parameter, in order to check the type of T.

Inferring the type of T just from the assignment might be helpful if you’re actually returning a generic object whose generic parameter is T. Have a look at Collections.emptyList() for example, which returns an empty List<T> (so there aren’t any elements in the list that are not of type T).

You could also set bounds for the T type:

public <T extends Number> T methodX() {
  return (T) someValue;
}

//would compile
Integer i = methodX();

//this would not compile, since s is not a number
String s = methodX();