Thread: Inheritance & Hierarchy Exercises?

Currently, I have only just started Java, and I am looking to elaborate more from my book to enforce what I am learning. As it stands, only two exercises remain in the Workshop section of this book, and I like to make firm my knowledge of a topic, so I would like to do some more exercises. Asked around on the gaming forum I was on, but then I decided to migrate to a specialized forum to maybe aid me in my triumphs with Java far more accurately. Sorry for the digression, but in any case, I am going to give the exercise from my book and maybe you guys can help give me some exercises similar.

Originally Posted by Exercise 2

Create an inheritance hierarchy for the pieces of a chess set. Decide where the instance variables color, startingPosition, forwardMovement, and sideMovement should be defined in the hierarchy.

Here's a code reference, if it helps at all. The first class (VolcanoRobot) is meant to be the superclass, and the second class (VolcanoApplication) is meant to be a subclass. My goal is to do some similar programs, on my own, instead of just reviewing and copying examples from a book. And even the one solo exercise it has me do, I want to do more to get a firm grasp of this, because I feel like inheritance will play a huge role in the future.

class VolcanoRobot {
    String status;
    int speed;
    float temperature;
 
    void checkTemperature() {
        if (temperature > 660) {
            status = "returing home";
            speed = 5;
        }
    }
 
    void showAttributes() {
        System.out.println("Status: " + status);
        System.out.println("Speed: " + speed);
        System.out.println("Temperature: " + temperature);
    }
}

class VolcanoApplication {
    public static void main(String[] arguments) {
        VolcanoRobot dante = new VolcanoRobot();
        dante.status = "exploring";
        dante.speed = 2;
        dante.temperature = 510;
 
        dante.showAttributes();
        System.out.println("Increasing speed to 3.");
        dante.speed = 3;
        dante.showAttributes();
        System.out.println("Changing temperature to 670.");
        dante.temperature = 670;
        dante.showAttributes();
        System.out.println("Checking the temperature.");
        dante.checkTemperature();
        dante.showAttributes();
    }
}

Help is much appreciated.

In your example code I don't see the super-class/sub-class relationship. What you have are two un-related classes in which one happens to use the other one. In order to have a super-class/sub-class relationship, you must use the extends keyword:

public class BaseClass
{
   // .. code
}
 
public class SubClass extends BaseClass
{
   // ..code
}

The best candidates for practicing inheritance are situations where you can say something is something. For example, consider shapes. A triangle is a shape. A rectangle is a shape. A circle is a shape. The shape class would provide several methods which makes sense for shapes, such as what is the area or perimeter of the shape, and where is the shape.

Side note:

You're directly accessing the fields of the VolcanoRobot class from the VolcanoApplication class. I would recommend that you get into the habit of using getter and setter methods and declare your fields private.

public class Class1
{
    private int someVal;
 
    public int getSomeVal()
    {
        return someVal;
    }
 
    public void setSomeVal(int value)
    {
        someVal = value;
    }
}