Why Java Lang.void cannot be serialized?

By default, the primitive 'void' can be serialized. Why can't the object 'void' extend serializable?

Add example:

Rootimplementation will have a compilation error saying "void is not in its scope" because it does not extend serializable Although 'somemethod' is declared as' void ', there will be no problem

public interface Root<R extends Serializable> extends Serializable {
  R someMethod();
}

public class RootImplementation implements Root<Void> {
  public Void someMethod() {
    return null;
  }
}

Solution

Well, in response to your example, if you change the method to void, it won't work because the method must have a return type (even if Java now allows covariant return types in rewriting methods) The invalid discussion confused the problem

What you want to do is declare a type parameter as "will only return null" Void is usually a good choice, but for void to work, the return type must be object Void cannot implement every interface in the API because someone might want to use it to indicate a null return of a type parameter

There are three ways to view your questions:

>Serializable is an overly strict type declaration You should really use object Do you really need it to be serializable? > You can declare the type parameter serializable and actually return null This doesn't exactly mean that you return null every time, but it may be enough. > You can declare your own class named null, which implements serializable, possibly as a static nested class of the root interface, and in this case use it as a type parameter You will find that it is not common to make your own null objects. There are (private) objects even in the standard JDK