Implement "wolf and sheep" task solution (#8)

Author: mperor

README.md

@@ -24,6 +24,7 @@ are not the only possible solutions to these cases.
     * [String Challenges 🔡](src/test/java/pl/mperor/interview/tasks/challenge/StringChallengeTest.java)
     * [Number Challenges 🔢](src/test/java/pl/mperor/interview/tasks/challenge/NumberChallengeTest.java)
 7. [Quiz Questions ❔](src/test/java/pl/mperor/interview/tasks/QuizQuestionsTest.java)
+8. [Wolf 🐺 & Sheep 🐑](src/test/java/pl/mperor/interview/tasks/exception/WolfFullAndSheepWholeTest.java)
 
 ## Sources 🔗
 

src/main/java/pl/mperor/interview/tasks/exception/Sheep.java

@@ -0,0 +1,22 @@
+package pl.mperor.interview.tasks.exception;
+
+class Sheep {
+
+    private boolean alive = true;
+
+    boolean isAlive() {
+        return alive;
+    }
+
+    void setAlive(boolean alive) {
+        this.alive = alive;
+    }
+
+    /**
+     * No matter what the sheep says, the wolf will eat it anyway.
+     * Unless the sheep offers something exceptionally good :)
+     */
+    boolean doesWantToBeEaten() {
+        return false;
+    }
+}

src/main/java/pl/mperor/interview/tasks/exception/SomethingExceptionallyGood.java

@@ -0,0 +1,8 @@
+package pl.mperor.interview.tasks.exception;
+
+class SomethingExceptionallyGood extends RuntimeException {
+
+    SomethingExceptionallyGood(String message) {
+        super(message);
+    }
+}

src/main/java/pl/mperor/interview/tasks/exception/Wolf.java

@@ -0,0 +1,21 @@
+package pl.mperor.interview.tasks.exception;
+
+class Wolf {
+
+    private boolean hungry = true;
+
+    boolean isHungry() {
+        return hungry;
+    }
+
+    void eat(Sheep sheep) {
+        sheep.setAlive(false);
+        hungry = false;
+        System.out.println("The wolf 🐺 devoured the sheep 🐑!");
+    }
+
+    void eat(SomethingExceptionallyGood something) {
+        hungry = false;
+        System.out.printf("The wolf 🐺 has eaten %s%n", something.getMessage());
+    }
+}

src/test/java/pl/mperor/interview/tasks/exception/WolfFullAndSheepWholeTest.java

@@ -0,0 +1,40 @@
+package pl.mperor.interview.tasks.exception;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class WolfFullAndSheepWholeTest {
+
+    @Test
+    public void shouldFeedWolfAndKeepSheepAlive() {
+        Wolf wolf = new Wolf();
+        Sheep sheep = new Sheep();
+        feedTheWolf(wolf, sheep, () -> {
+            // Todo: Try to save sheep!
+            throw new SomethingExceptionallyGood("candies 🍬");
+        });
+        Assertions.assertTrue(!wolf.isHungry() && sheep.isAlive(), "The wolf should not be hungry and the sheep alive!");
+    }
+
+    /**
+     * The wolf should eat the sheep. However, if we offer something exceptionally good,
+     * the wolf may choose to go for it instead.
+     * <p>
+     * Handle this exceptional situation appropriately.
+     * Do not modify the existing code.
+     */
+    private static void feedTheWolf(Wolf wolf, Sheep sheep, Runnable doSomethingToSaveSheep) {
+        try {
+            boolean willEatSheep = sheep.doesWantToBeEaten();
+            if (willEatSheep || !willEatSheep) { // actually, the sheep has no say
+                doSomethingToSaveSheep.run();
+                wolf.eat(sheep);
+            }
+        } catch (SomethingExceptionallyGood something) {
+            wolf.eat(something);
+        } finally {
+            assert !wolf.isHungry();
+        }
+    }
+
+}