Question

I have an abstract superclass that has a protected String variable. It is not initialized in the superclass.

All I want to do is initialize and use it in a subclass. So, I have something like this:

    public class MySubclass extends MyAbstractSuperclass {        
        thing = "i'm a thing";
        [...]
    }

Seems simple enough, since the whole point of inheritance is reusing classes and their fields in different contexts. But that is wrong: Syntax error on token "thing", VariableDeclaratorId expected after this token.

I can get it to compile by putting brackets around the subclass initialization. What I would like to know is why the first way is wrong, and why brackets fix it. Thanks for any help.

edit: I appreciate the tip that I can fix this by using a constructor. However, I am still curious as to what is actually wrong with using a superclass field in this way, as it seems to me to be pretty intuitive. And also, why do the braces fix it, what exactly does it mean to surround a statement with braces like that outside of e.g. a loop structure?

Answer 1

What I would like to know is why the first way is wrong, and why brackets fix it. Thanks for any help.

public class MySubclass extends MyAbstractSuperclass {        
    thing = "i'm a thing";
    [...]
}

You try to do a statement here, set the value of the variable thing to text. You can not do statements here, you can only do variable declaration here.

public class MySubclass extends MyAbstractSuperclass { 
    {       
        thing = "i'm a thing";
    }
    [...]
}

Now, you have a initializer block, this one is executed as a statement (before the constructor). Therefore, you can access thing, because visibility is protected. See for example here: http://docs.oracle.com/javase/tutorial/java/javaOO/initial.html