访问超类中方法的变量

Question

I have a basic code with an Animal class and a Dog and a Cat subclass. I have a speak method. The speak method receives a string, and returns a string in cat and dog "language". If a character's ascii code is even, it returns "uff", if not, "vau". When I override the method, I want to set oddSound and evenSound from the Dog class, but I can't find a proper way to do this.
This code is from the Animal class:

public String speak(String what){
    String speakableString = new String();
    String oddSound = new String();
    String evenSound = new String();

    for (int i = 0; i < what.length(); i++) {
        if((((int) what.charAt(i)) & 1) == 1){ 
            speakableString.concat(oddSound); 
        }else if ((((int) what.charAt(i)) & 1) == 0){
            speakableString.concat(evenSound);
        }
    }

    speakableString = speakableString.substring(0, speakableString.length()-1);
    return speakableString;
}

This code is from the Dog class:

public String speak(String what){
    //set oddSound = "vau"
    //set evenSound = "uff"
    return super.speak(what);
}

Answer 1

In the Animal class, have two protected fields,

protected String oddSound;
protected String evenSound;

Then, in the Dog and Cat classes, you can set these fields:

oddSound = "woof";
evenSound = "woofwoof"

Then, in the speak() method, you can simply use this.oddSound and this.evenSound

Answer 2

The Animal class should declare your speak method, since that is common to both the Dog and Cat classes.

public class Animal {
    String oddSound;
    String evenSound;

    public Animal(String oddSound, String evenSound) {
        this.oddSound = oddSound;
        this.evenSound = evenSound;
    }

    public String speak(String what){
        String speakableString = new String();

        for (int i = 0; i < what.length(); i++) {
            if((((int) what.charAt(i)) & 1) == 1){ 
                speakableString = speakableString.concat(oddSound); 
            }else if ((((int) what.charAt(i)) & 1) == 0){
                speakableString = speakableString.concat(evenSound);
            }
        }

    speakableString = speakableString.substring(0, speakableString.length()-1);
    return speakableString;
    }
}

Keep in mind that the string.concat method creates a new object, it does not modify the instance on which it's called. See String API Documentation

Your Dog and Cat classes should define or override methods only as needed. It seems all you're doing in their speak method is calling the super method implementation. You can get rid of that completely.

If you want to extend the Animal class to provide new methods or implementations, do it like this:

public class Dog extends Animal {
    public Dog() {
        // This calls the super constructor, which sets the oddSound and evenSound fields
        super("vau", "uff");
    }

    // This section does nothing.
    // A method implementation which only calls its super implementation is ineffective.
    // If you were to provide a new implementation, this is where it would be.
    //public String speak(String what) {
    //  super.speak(what);  
    //}
}

Answer 3

You can keep them as data members, and set them in the respective constructors:

public class Animal {
    private String oddSound;
    private String evenSound;

    protected Animal (String oddSound, String evenSound) {
        this.oddSound = oddSound;
        this.evenSound = evenSound;
    }

    public String speak(String what){
        String speakableString = new String();

        for (int i = 0; i < what.length(); i++) {
            if((((int) what.charAt(i)) & 1) == 1){ 
                speakableString = speakableString.concat(oddSound); 
            }else if ((((int) what.charAt(i)) & 1) == 0){
                speakableString = speakableString.concat(evenSound);
            }
        }
}

public class Dog extends Animal {
    public Dog() {
        super ("uff", "vau");
    }
}

Answer 4

You could break up your speak implementation in to two parts to allow you to pass in the Strings that you want to use for oddSound and evenSound .

public String speak(String what){
    return getSpeakableString(what, new String(), new String());
}
protected String getSpeakableString(String what, String oddSound, String evenSound){
    //this is just copied from what you had in your question, it likely doesn't do what you actually want.
    String speakableString = new String();
    for (int i = 0; i < what.length(); i++) {
        if((((int) what.charAt(i)) & 1) == 1){ 
            speakableString.concat(oddSound); 
        }else if ((((int) what.charAt(i)) & 1) == 0){
            speakableString.concat(evenSound);
        }
    }
    speakableString = speakableString.substring(0, speakableString.length()-1);
    return speakableString;
}

//in subclass
@Override
public String speak(String what){
    return getSpeakableString(what, "vau", "uff");
}