8264779: Fix doclint warnings in java/nio

Reviewed-by: chegar, iris, alanb, naoto

src/java.base/share/classes/java/nio/file/DirectoryIteratorException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -73,9 +73,19 @@ public final class DirectoryIteratorException
     /**
      * Called to read the object from a stream.
      *
+     * @param   s
+     *          the {@code ObjectInputStream} to read
+     *
      * @throws  InvalidObjectException
      *          if the object is invalid or has a cause that is not
      *          an {@code IOException}
+     *
+     * @throws  IOException
+     *          if an I/O error occurs
+     *
+     * @throws  ClassNotFoundException
+     *          if the class of a serialized object could not be
+     *          found
      */
     @java.io.Serial
     private void readObject(ObjectInputStream s)

src/java.base/share/classes/java/nio/file/FileSystemException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -40,7 +40,15 @@ public class FileSystemException
     @java.io.Serial
     static final long serialVersionUID = -3055425747967319812L;
 
+    /**
+     *  String identifying the file or {@code null} if not known.
+     */
     private final String file;
+
+    /**
+     *  String identifying the other file or {@code null} if there isn't
+     *  another file or if not known.
+     */
     private final String other;
 
     /**

src/java.base/share/classes/java/nio/file/InvalidPathException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -39,7 +39,15 @@ public class InvalidPathException
     @java.io.Serial
     static final long serialVersionUID = 4355821422286746137L;
 
+    /**
+     * The input string.
+     */
     private String input;
+
+    /**
+     * The index of the input string at which the error occurred or
+     * {@code -1} if not known.
+     */
     private int index;
 
     /**

src/java.base/share/classes/java/nio/file/attribute/UserPrincipalNotFoundException.java

@@ -40,6 +40,9 @@ public class UserPrincipalNotFoundException
     @java.io.Serial
     static final long serialVersionUID = -5369283889045833024L;
 
+    /**
+     * The user principal name.
+     */
     private final String name;
 
     /**