Are composites of serializable objects also serializable?

Question

If I have a serializable type e.g. String and make a class

class Tuple {

  String s1 = "Hello";
  String s2 = "World";

}

Then will this class also be serializable because both strings are, or will it not be serializable because it doesn't implement the serializable interface?

Answer 1

No, it won't. Class implementing Serializable interface can be serialized. Not a class having has-a relationship with Serializable class objects.

You may like to read about Serializable here.

Answer 2

No, your class must implement Serializable interface. Java does not make such bottom-to-top assumptions about the data.

class Tuple implements Serializable {

    private static final long serialVersionUID = 5316748056989930874L;

    //whatever
}