Fixing javadocs

Change-Id: I8e7f6451876c6733bf33667face30b32e5378c99

@@ -88,7 +88,7 @@ public abstract class AbstractProjectableModel extends AbstractModel implements
     }
     }
 
 
     /**
     /**
-     * Returns the currently bound driver or null of no driver is bound.
+     * Returns the currently bound driver or null if no driver is bound.
      *
      *
      * @return bound driver; null if none
      * @return bound driver; null if none
      */
      */

@@ -30,7 +30,9 @@ public interface Projectable {
      *
      *
      * @param projectionClass requested projection class
      * @param projectionClass requested projection class
      * @param <B> type of behaviour
      * @param <B> type of behaviour
-     * @return projection instance or null if requested projection is not supported
+     * @return projection instance
+     * @throws IllegalStateException if a driver cannot be found
+     * @throws IllegalArgumentException if the projection is not supported
      */
      */
     <B extends Behaviour> B as(Class<B> projectionClass);
     <B extends Behaviour> B as(Class<B> projectionClass);