Question

I would like to declare a data member of a superclass, private:

public abstract class superclass {
  private int verySensitive;

  abstract int setVerySensitive(int val); // must be overriden by subclass to work properly
}


public class subclass extends superclass {

  @Override
  protected int setVerySensitive(int val) {
    if (val > threshLow && val < threshHigh) // threshHigh is calculated in superclass constructor
       verySensitive = val;
  }
}

As you can see, I have a problem here: superclass can’t access verySensitive because it’s private, but I don’t want to make verySensitive protected because it’s… sensitive.

Also note that setVerySensitive was made abstract because checking against valid values can only be done after superclass has been constructed.

Can you recommend an elegant way of getting out of this “catch 22” situation?

Answer 1

I suggest something like this:

public abstract class superclass {
  private int verySensitive;

  final int setVerySensitive(int val) {
    if (checkVerySensitive(val)) {
      verySensitive = val;
    }
  }
  protected abstract boolean checkVerySensitive(int val);
}


public class subclass extends superclass {

  @Override
  protected boolean checkVerySensitive(int val) {
    return val > threshLow && val < threshHigh; // threshHigh is calculated in superclass constructor
  }
}

This is similar to EboMike’s suggestion, but it leaves setVerySensitive(int) with package access instead of making it private.