Question

I have following problem;

I have inerface with public method clone():

public interface Something {
    Something clone();
}

and also

public class SomethingImpl implements Something {

        private Something some;

    public Something clone() {
        return some.clone();
    }
}

Whenewer I run from code somewhere

...
Something i =  new SomethingImpl();
...
// do something on i
...
someMethod(i);
...

public void someMethod(Something some){
    Something some2 = some.clone(); 
  }

I get Exception in thread “main” java.lang.NullPointerException on line Someting some2 = some.clone;

I programmed a lot bussiness logic, but never till now I encountered neccessity of cloning, esspecially this way.

Can someone point me in which direction I should go? I tried to read articles on this topic but just got more confused.

Thanks in advance,
Mile

Answer 1

A method and a field are two different things. clone is a field, which is not defined and hence will not exist. clone() is a method. Did you mean Someting some2 = some.clone()?

Edit I just saw your actual error (although what I said above should still be heeded!). This means that some must be null – are you perhaps changing its value in the portions of code you omitted? Be sure to check for that whenever you receive a NullPointerException.