added ex T

src/exercises/Utils.java

@@ -0,0 +1,7 @@
+package exercises;
+
+public class Utils {
+    public static void randomSleep(long min, long max) throws InterruptedException {
+        Thread.sleep((long) (min + Math.random() * max));
+    }
+}

src/exercises/ex_t/BowlSemaphore.java

@@ -0,0 +1,24 @@
+package exercises.ex_t;
+
+import java.util.concurrent.Semaphore;
+
+public class BowlSemaphore {
+    private boolean isFull = false;
+    private Semaphore semaphore = new Semaphore(1);
+
+    public boolean fill() throws InterruptedException {
+        semaphore.acquire();
+        boolean wasFull = isFull;
+        isFull = true;
+        semaphore.release();
+        return wasFull;
+    }
+
+    public boolean empty() throws InterruptedException {
+        semaphore.acquire();
+        boolean wasFull = isFull;
+        isFull = false;
+        semaphore.release();
+        return wasFull;
+    }
+}

src/exercises/ex_t/Dog.java

@@ -0,0 +1,29 @@
+package exercises.ex_t;
+
+import exercises.Utils;
+
+public class Dog implements Runnable {
+    private final String name;
+    private final BowlSemaphore[] bowls;
+
+    public Dog(String name, BowlSemaphore[] bowls) {
+        this.name = name;
+        this.bowls = bowls;
+    }
+
+    @Override
+    public void run() {
+        while (true) {
+            for (int i = 0; i < 3; i++) {
+                BowlSemaphore bowl = bowls[i];
+                try {
+                    if (bowl.empty()) {
+                        System.out.println(name + " ate from bowl " + i);
+                        Utils.randomSleep(10000, 20000);
+                        break;
+                    }
+                } catch (InterruptedException _) {}
+            }
+        }
+    }
+}

src/exercises/ex_t/Feeder.java

@@ -0,0 +1,28 @@
+package exercises.ex_t;
+
+import exercises.Utils;
+
+public class Feeder implements Runnable {
+    private final String name;
+    private final BowlSemaphore[] bowls;
+
+    public Feeder(String name, BowlSemaphore[] bowls) {
+        this.name = name;
+        this.bowls = bowls;
+    }
+
+    @Override
+    public void run() {
+        while (true) {
+            for (int i = 0; i < 3; i++) {
+                BowlSemaphore bowl = bowls[i];
+                try {
+                    if (!bowl.fill()) {
+                        System.out.println(name + " filled bowl " + i);
+                        Utils.randomSleep(1000, 3000);
+                    }
+                } catch (InterruptedException _) {}
+            }
+        }
+    }
+}

src/exercises/ex_t/TestingSemaphore_DogBreeder.java

@@ -0,0 +1,16 @@
+package exercises.ex_t;
+
+public class TestingSemaphore_DogBreeder {
+    public static void main(String[] args) {
+        BowlSemaphore[] bowlsSemaphores = new BowlSemaphore[3];
+        for (int i = 0; i < 3; i++) {
+            bowlsSemaphores[i] = new BowlSemaphore();
+        }
+
+        new Thread(new Feeder("Marco", bowlsSemaphores)).start();
+        new Thread(new Feeder("Luisa", bowlsSemaphores)).start();
+        for (int i = 1; i < 10; i++) {
+            new Thread(new Dog("Dog" + i, bowlsSemaphores)).start();
+        }
+    }
+}