Annotate assorted new APIs.

src/java.base/share/classes/java/lang/String.java

@@ -4480,7 +4480,7 @@ public String translateEscapes() {
      *
      * @since 12
      */
-    public <R> R transform(Function<? super String, ? extends R> f) {
+    public <R extends @Nullable Object> R transform(Function<? super String, ? extends R> f) {
         return f.apply(this);
     }
 
@@ -4651,7 +4651,7 @@ public static String format( @Nullable Locale l, String format,  @Nullable Objec
      * @since 15
      *
      */
-    public String formatted(Object... args) {
+    public String formatted(@Nullable Object... args) {
         return new Formatter().format(this, args).toString();
     }
 

src/java.base/share/classes/java/lang/ref/Reference.java

@@ -376,7 +376,7 @@ public <T> ReferenceQueue<T> newNativeReferenceQueue() {
      * @return {@code true} if {@code obj} is the referent of this reference object
      * @since 16
      */
-    public final boolean refersTo(T obj) {
+    public final boolean refersTo(@Nullable T obj) {
         return refersToImpl(obj);
     }
 

src/java.base/share/classes/java/lang/reflect/InvocationHandler.java

@@ -260,7 +260,7 @@ public interface InvocationHandler {
      * @jvms 5.4.3 Resolution
      */
     @CallerSensitive
-    public static Object invokeDefault(Object proxy, Method method, Object... args)
+    public static Object invokeDefault(Object proxy, Method method, @Nullable Object @Nullable ... args)
             throws Throwable {
         Objects.requireNonNull(proxy);
         Objects.requireNonNull(method);

src/java.base/share/classes/java/nio/charset/Charset.java

@@ -585,8 +585,8 @@ public static Charset forName(String charsetName) {
      *
      * @since 18
      */
-    public static Charset forName(String charsetName,
-                                  Charset fallback) {
+    public static @Nullable Charset forName(String charsetName,
+                                  @Nullable Charset fallback) {
         try {
             Charset cs = lookup(charsetName);
             return cs != null ? cs : fallback;