我们如何在java中创建类Object类

Question

在java中，默认情况下，每个类都扩展了Object ，就像我们如何使我们的类A可以在我们的应用程序中默认扩展。

Answer 1

The short answer - you can't.

The slightly longer answer - you can create you own custom empty class...

public class MyObject {
}

.. and make every class in your project extend it...

public class MyOtherClass extends MyObject {
    public int doStuff();
}

... but it's really unlikely there'll be any (good) use for this.

Answer 2

No. The class that other classes extend by default is Object . You cannot change that. It is a fundamental part of the Java language.

The JLS 8.1.4 says:

Given a (possibly generic) class declaration C<F1,...,Fn> (n ≥ 0, C ≠ Object) , the direct superclass of the class type C<F1,...,Fn> is the type given in the extends clause of the declaration of C if an extends clause is present, or Object otherwise.

There is no "wriggle room".

---

If you want all of the classes in your applications to be subclasses of something other than Object , then you must have an extends clause on each and every one of them.

Answer 3

You cannot define an own class as a replacement for the Object class.

You can however create your own base class and let all your classes extend from that base class.

Answer 4

Answer: You Cannot !!

• Object class is the parent of all the classes in java

• What ever classes you use is a subclass of object class by default

• You can guarantee there will always be certain methods, like toString() , equals() , hashCode() , etc.

• It helps in synchronization , garbage collection etc

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Why it is like this:

Java is designed this way so Object class helps by providing all the above mentioned and more features which are fundamental for object communication and object identifying so to have these functionality explicitly extending a class not required

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More information:

1. Have a look at this Stackoverflow answer here
2. Oracle Docs
3. Grep Code

Answer 5

There's no way to do that.

You just have to explicitly make every class extend A. like so

public class B extends A {

}

Answer 6

The answer is you can't.

Object class is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.

Answer 7

It's certainly impossible to do it without explicitly using extends . Object is the parent class of every Java Class , so I think you'll need to stick to it. Apart from that, you can always extend a class with the one you like.

Hope it helps.

Clemencio Morales Lucas.