Javadoc improvements.

core/src/main/java/hudson/model/AbstractProject.java

@@ -1099,7 +1099,10 @@ public abstract class AbstractProject<P extends AbstractProject<P,R>,R extends A
     }
 
     /**
-     * Determines Class&lt;R>.
+     * Type token for the corresponding build type.
+     * The build class must have two constructors:
+     * one taking this project type;
+     * and one taking this project type, then {@link File}.
      */
     protected abstract Class<R> getBuildClass();
 

core/src/main/java/hudson/model/Executor.java

@@ -274,13 +274,13 @@ public class Executor extends Thread implements ModelObject {
     }
 
     /**
-     * Returns the current {@link hudson.model.Queue.Task} this executor is running.
+     * Returns the current build this executor is running.
      *
      * @return
      *      null if the executor is idle.
      */
     @Exported
-    public Queue.Executable getCurrentExecutable() {
+    public @CheckForNull Queue.Executable getCurrentExecutable() {
         return executable;
     }