added play-framework project (#678)

* made changes to java reflection

* removed redundant method makeSound in Animal abstract class

* added project for play-framework article

play-framework/student-api/app/services/AtomicCounter.java

@@ -0,0 +1,26 @@
+package services;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.inject.*;
+
+/**
+ * This class is a concrete implementation of the {@link Counter} trait.
+ * It is configured for Guice dependency injection in the {@link Module}
+ * class.
+ *
+ * This class has a {@link Singleton} annotation because we need to make
+ * sure we only use one counter per application. Without this
+ * annotation we would get a new instance every time a {@link Counter} is
+ * injected.
+ */
+@Singleton
+public class AtomicCounter implements Counter {
+
+    private final AtomicInteger atomicCounter = new AtomicInteger();
+
+    @Override
+    public int nextCount() {
+       return atomicCounter.getAndIncrement();
+    }
+
+}