diff --git a/src/java.base/share/classes/java/lang/Thread.java b/src/java.base/share/classes/java/lang/Thread.java
index 414d0ce7bae..73d96cd5cfe 100644
--- a/src/java.base/share/classes/java/lang/Thread.java
+++ b/src/java.base/share/classes/java/lang/Thread.java
@@ -1158,7 +1158,7 @@ public Thread() {
      *
      * @see <a href="#inheritance">Inheritance when creating threads</a>
      */
-    public Thread(Runnable task) {
+    public Thread(@Nullable Runnable task) {
         this(null, null, 0, task, 0, null);
     }
 
@@ -1268,7 +1268,7 @@ public Thread(@Nullable ThreadGroup group, String name) {
      *
      * @see <a href="#inheritance">Inheritance when creating threads</a>
      */
-    public Thread(Runnable task, String name) {
+    public Thread(@Nullable Runnable task, String name) {
         this(null, checkName(name), 0, task, 0, null);
     }
 
@@ -1322,7 +1322,7 @@ public Thread(Runnable task, String name) {
      *
      * @see <a href="#inheritance">Inheritance when creating threads</a>
      */
-    public Thread(@Nullable ThreadGroup group, Runnable task, String name) {
+    public Thread(@Nullable ThreadGroup group, @Nullable Runnable task, String name) {
         this(group, checkName(name), 0, task, 0, null);
     }
 
@@ -1469,7 +1469,7 @@ public Thread(@Nullable ThreadGroup group, @Nullable Runnable task, String name,
      * @since 9
      * @see <a href="#inheritance">Inheritance when creating threads</a>
      */
-    public Thread(ThreadGroup group, Runnable task, String name,
+    public Thread(@Nullable ThreadGroup group, @Nullable Runnable task, String name,
                   long stackSize, boolean inheritInheritableThreadLocals) {
         this(group, checkName(name),
                 (inheritInheritableThreadLocals ? 0 : NO_INHERIT_THREAD_LOCALS),
diff --git a/src/java.prefs/share/classes/java/util/prefs/AbstractPreferences.java b/src/java.prefs/share/classes/java/util/prefs/AbstractPreferences.java
index 459432b84f5..10ec45a78c1 100644
--- a/src/java.prefs/share/classes/java/util/prefs/AbstractPreferences.java
+++ b/src/java.prefs/share/classes/java/util/prefs/AbstractPreferences.java
@@ -200,7 +200,7 @@ public abstract class AbstractPreferences extends Preferences {
      *          ({@code '/'}),  or {@code parent} is {@code null} and
      *          name isn't {@code ""}.
      */
-    protected AbstractPreferences(AbstractPreferences parent, String name) {
+    protected AbstractPreferences(@Nullable AbstractPreferences parent, String name) {
         if (parent==null) {
             if (!name.isEmpty())
                 throw new IllegalArgumentException("Root name '"+name+