is there a way to add a default constructor to an interface

问题

With default methods now added to Java 8, is there any way to create a default constructor?

I've tried:

public interface KadContent<T>
{
    public default KadContent()
    {

    }
...

Getting the error <identifier> expected from Netbeans

Why Needed? I'm using Gson to serialize the objects and getting the "unable to invoke no-args constructor .." error and I do know that I can resolve this problem using Gson's InstanceCreator. But is there a way to create a default Constructor?

Update

I've found the problem with my own code. I was using

gson.fromJson(new String(data), InterfaceName.class);

instead of

gson.fromJson(new String(data), ClassName.class);

So even though the subclass had default constructors, the deserialization code was incorrect. But the question of default constructor still stands.

回答1:

No, this is not possible.

1. It does not make sense in an interface
2. If you implement an interface, the class has already a default constructor (the one without arguments)

You may want to use an abstract class if you want implementations have a "default constructor".

回答2:

It does not make sense to provide an Constructor in an Interface.

Check if it makes sense for you to provide a default initialize() method instead.

回答3:

Constructors are when the objects come into picture and the fact that a object for an interface cannot be constructed is SOUND, be it Java, C# or Java8

So... if you have any functionality that you would want to define by default in the interface level, Java8 introduces the concept of Default Methods.

回答4:

You need to add the default constructor to the class you want to serialize.

回答5:

Yes, kind of! You can do:

public interface MyInterface {
  MyInterface NO_OP = new MyInterface() {};
}

来源：https://stackoverflow.com/questions/22810921/is-there-a-way-to-add-a-default-constructor-to-an-interface