Unit 13 - Interacting classes

Topics:

• class relationships
  • inheritance == ‘is a’
  • composition == ‘has a’
• interacting classes
• computations on member lists

Assignment

Cat.java
CatCollection.java

//
// Cat.java
//


public class Cat
{
    public Cat(String name, String color, int fleaCount)
    {
        this.name = name;
        this.color = color;
        this.fleaCount = fleaCount;
    }

    public String getName() {return name;}
    public String getColor() {return color;}
    public int getFleaCount() {return fleaCount;}

    public String toString() 
    {
        return name + "[" + color + "," + fleaCount + "]";
    }

    private String name;
    private String color;
    private int fleaCount;
}

//
// CatCollection.java
//


import java.util.*;


public class CatCollection
{
    public CatCollection()
    {
        cats = new ArrayList<Cat>();
    }
    
    public void adoptCat(String name, String color, int fleaCount)
    {
        cats.add(new Cat(name, color, fleaCount)); 
    }

    public void callToDinner()
    {
        for (Cat c : cats)
        {
            System.out.println("Dinner time " + c.getName() + "!");
        }
    }

    public ArrayList<Cat> getBlackCatList()
    {
        ArrayList<Cat> result = new ArrayList<Cat>();

        for (Cat c : cats)
            if (c.getColor().equals("Black"))
                result.add(c);

        return result;
    }


    public double getFleaDensity()
    {
        double total = 0;

        for (Cat c : cats)
            total += c.getFleaCount();

        return total / cats.size();
    }

    private ArrayList<Cat> cats;


    /////////////////

    public static void main(String[] args)
    {
        CatCollection herd = new CatCollection();
        herd.adoptCat("Midnight", "Black", 3);
        herd.adoptCat("Kitty", "Orange", 1);
        herd.adoptCat("Zippy", "Black", 0);

        herd.callToDinner();

        ArrayList<Cat> blackCats = herd.getBlackCatList();
        System.out.println(blackCats);

        System.out.println("flea density: " + herd.getFleaDensity());
    }
}

Ball.java
BallGenerator.java
BallDemo.java

notes (pdf)