Address some https://errorprone.info/bugpattern/ProtectedMembersInFinalClass findings.

RELNOTES=n/a
PiperOrigin-RevId: 813888825

Author: cpovirk

jimfs/src/main/java/com/google/common/jimfs/JimfsSecureDirectoryStream.java

@@ -79,7 +79,7 @@ public synchronized void close() {
     fileSystemState.unregister(this);
   }
 
-  protected synchronized void checkOpen() {
+  synchronized void checkOpen() {
     if (!open) {
       throw new ClosedDirectoryStreamException();
     }

jimfs/src/main/java/com/google/common/jimfs/PathService.java

@@ -175,7 +175,7 @@ public JimfsPath createPath(@Nullable Name root, Iterable<Name> names) {
   }
 
   /** Returns a path with the given root (or no root, if null) and the given names. */
-  protected final JimfsPath createPathInternal(@Nullable Name root, Iterable<Name> names) {
+  final JimfsPath createPathInternal(@Nullable Name root, Iterable<Name> names) {
     return new JimfsPath(this, root, names);
   }
 

jimfs/src/test/java/com/google/common/jimfs/PathSubject.java

@@ -55,7 +55,7 @@ public static Subject.Factory<PathSubject, Path> paths() {
   private static final LinkOption[] NOFOLLOW_LINKS = {LinkOption.NOFOLLOW_LINKS};
 
   private final Path actual;
-  protected LinkOption[] linkOptions = FOLLOW_LINKS;
+  LinkOption[] linkOptions = FOLLOW_LINKS;
   private Charset charset = UTF_8;
 
   private PathSubject(FailureMetadata failureMetadata, Path subject) {