--- a/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/internal/dynalink/support/CompositeTypeBasedGuardingDynamicLinker.java	Mon Oct 19 08:39:06 2015 +0200
+++ b/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/internal/dynalink/support/CompositeTypeBasedGuardingDynamicLinker.java	Mon Oct 19 08:45:29 2015 +0200
@@ -87,6 +87,7 @@
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Objects;
 import jdk.internal.dynalink.linker.GuardedInvocation;
 import jdk.internal.dynalink.linker.GuardingDynamicLinker;
 import jdk.internal.dynalink.linker.LinkRequest;
@@ -94,10 +95,12 @@
 import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;
 
 /**
- * A composite type-based guarding dynamic linker. When a receiver of a not yet seen class is encountered, all linkers
- * are queried sequentially on their {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} method. The linkers
- * returning true are then bound to the class, and next time a receiver of same type is encountered, the linking is
- * delegated to those linkers only, speeding up dispatch.
+ * A composite type-based guarding dynamic linker. When a receiver of a not yet
+ * seen class is encountered, all linkers are queried sequentially on their
+ * {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} method. The linkers
+ * returning true are then bound to the class, and next time a receiver of same
+ * type is encountered, the linking is delegated to those linkers only, speeding
+ * up dispatch.
  */
 public class CompositeTypeBasedGuardingDynamicLinker implements TypeBasedGuardingDynamicLinker, Serializable {
     private static final long serialVersionUID = 1L;
@@ -149,15 +152,24 @@
      * Creates a new composite type-based linker.
      *
      * @param linkers the component linkers
+     * @throws NullPointerException if {@code linkers} or any of its elements
+     * are null.
      */
     public CompositeTypeBasedGuardingDynamicLinker(final Iterable<? extends TypeBasedGuardingDynamicLinker> linkers) {
         final List<TypeBasedGuardingDynamicLinker> l = new LinkedList<>();
         for(final TypeBasedGuardingDynamicLinker linker: linkers) {
-            l.add(linker);
+            l.add(Objects.requireNonNull(linker));
         }
         this.classToLinker = new ClassToLinker(l.toArray(new TypeBasedGuardingDynamicLinker[l.size()]));
     }
 
+    /**
+     * Returns true if any of the composite linkers return true from
+     * {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} for the type.
+     * @param type the type to link
+     * @return true if any of the composite linkers can link calls for the
+     * receiver type, false otherwise.
+     */
     @Override
     public boolean canLinkType(final Class<?> type) {
         return !classToLinker.get(type).isEmpty();
@@ -180,17 +192,21 @@
     }
 
     /**
-     * Optimizes a list of type-based linkers. If a group of adjacent linkers in the list all implement
-     * {@link TypeBasedGuardingDynamicLinker}, they will be replaced with a single instance of
+     * Optimizes a list of type-based linkers. If a group of adjacent linkers in
+     * the list all implement {@link TypeBasedGuardingDynamicLinker}, they will
+     * be replaced with a single instance of
      * {@link CompositeTypeBasedGuardingDynamicLinker} that contains them.
      *
      * @param linkers the list of linkers to optimize
      * @return the optimized list
+     * @throws NullPointerException if {@code linkers} or any of its elements
+     * are null.
      */
     public static List<GuardingDynamicLinker> optimize(final Iterable<? extends GuardingDynamicLinker> linkers) {
         final List<GuardingDynamicLinker> llinkers = new LinkedList<>();
         final List<TypeBasedGuardingDynamicLinker> tblinkers = new LinkedList<>();
         for(final GuardingDynamicLinker linker: linkers) {
+            Objects.requireNonNull(linker);
             if(linker instanceof TypeBasedGuardingDynamicLinker) {
                 tblinkers.add((TypeBasedGuardingDynamicLinker)linker);
             } else {