Why to override clone method in Java

Question

I am confused regarding overriding clone method in the class for which I want cloned object.

Object class has protected object method and as per the protected behavior which is When a method is protected, it can only be accessed by the class itself, subclasses of the class, or classes in the same package as the class.

As every class in Java extends from Object, so it should have clone method but still we are forced to override clone. Why is it required?

Also, I have read at some places to override the clone object and make it public. I wonder, why is it so?

All answers are welcome.

Answer 1

As every class in Java extends from Object, so it should have clone method but still we are forced to override clone

No you are not forced to override the clone method. In inheritance, when you inherit a class, you are not forced to override it's method. Its modifier being public or protected doesn't make much of a difference. However, if you want to invoke a method directly on super class reference, then that method has to be public. Protected methods are accessible only through inheritance. That is you can only access them through subclass reference. Or if you override the method, you can access them through super keyword.

Having said that, you should not override clone method, as it is broken. Because, for a class to be cloned, you need to implement the Cloneable interface. And then your class uses the clone method of Object class instead. Because, Cloneable interface doesn't exactly have any method for cloning. It would be a better option to use Copy Constructor instead.

public class A {
   private int data;
   public A() {
   }

   public A(A a) {
      this.data = a.data;
   }
}

For more details, I would suggest to go through this chapter of Joshua Bloch's Effective Java, which covers all aspects of using clone method.

Effective Java- Item # 11 - Override clone judiciously