Klasy i ich dziedziczenie

Author: Andrew Longosz

Animal.class

@@ -0,0 +1,17 @@
+public abstract class Animal extends Organism {
+    private final int legs;
+
+    public Animal(int legs) {
+        super();
+        this.legs = legs;
+        System.out.println("Creating animal...");
+    }
+
+    public void eat(Plant plant) {
+        System.out.printf("%s is eating %s\n", this, plant);
+    }
+
+    public int getLegs() {
+        return legs;
+    }
+}

Animal.java

@@ -0,0 +1,6 @@
+public class Grass extends Plant {
+    public Grass() {
+        super();
+        System.out.println("Creating grass...");
+    }
+}

Grass.class

@@ -0,0 +1,6 @@
+public class Hay extends Grass {
+    public Hay() {
+        super();
+        System.out.println("Creating hay...");
+    }
+}

Grass.java

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+public class Horse extends Animal {
+    public Horse() {
+        super(4);
+        System.out.println("Creating a horse...");
+    }
+}

Hay.class

@@ -0,0 +1,8 @@
+World: *.java
+	javac *.java
+
+clean:
+	rm -f *.class
+
+IDE:
+	vim World.java -c 'sp Animal.java' -c 'vsp Spider.java'

Hay.java

@@ -0,0 +1,29 @@
+import java.util.Map;
+import java.util.HashMap;
+
+public abstract class Organism {
+    private static int counter = 0;
+    private static Map<String, Integer> specificCounter = new HashMap<String, Integer>();
+
+    public Organism() {
+        System.out.println("Creating an organism...");
+        ++counter;
+        String specificName = toString();
+        if (!specificCounter.containsKey(specificName)) {
+            specificCounter.put(specificName, 0);
+        }
+        specificCounter.put(specificName, specificCounter.get(specificName) + 1);
+    }
+
+    public static int getCounter() {
+        return counter;
+    }
+
+    public static int getSpecificCounter(Organism o) {
+        return specificCounter.get(o.toString());
+    }
+
+    public String toString() {
+        return getClass().getName();
+    }
+}

Horse.class

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+public abstract class Plant extends Organism {
+    public Plant() {
+        super();
+        System.out.println("Creating a plant...");
+    }
+}

Horse.java

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+public class Spider extends Animal {
+    public Spider() {
+        super(8);
+        System.out.println("Creating a spider...");
+    }
+}

Makefile

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+public class World {
+    public static void main(String[] args) {
+        Spider spider = new Spider();
+        Grass grass = new Grass();
+        Hay hay = new Hay();
+        final int herdCount = 10;
+        Horse[] herd = new Horse[herdCount];
+
+        spider.eat(grass);
+
+        for (int i = 0; i < herdCount; ++i) {
+            herd[i] = new Horse();
+        }
+
+        Horse myHorse = herd[4];
+
+        for (Horse horse : herd) {
+            horse.eat(hay);
+        }
+
+
+        int c = Organism.getCounter();
+        if (c == 1) {
+            System.out.printf("There is 1 organism\n");
+        } else {
+            System.out.printf("There are %d ogranisms\n", c);
+        }
+
+        int hc = Horse.getSpecificCounter(myHorse);
+        System.out.printf("There are %d horses\n", hc);
+        System.out.printf("A %s has %d legs\n", spider, spider.getLegs());
+        System.out.printf("A %s has %d legs\n", myHorse, myHorse.getLegs());
+    }
+}