--- a/langtools/src/share/classes/com/sun/tools/doclets/internal/toolkit/Configuration.java	Fri Oct 05 14:16:32 2012 -0700
+++ b/langtools/src/share/classes/com/sun/tools/doclets/internal/toolkit/Configuration.java	Fri Oct 05 14:21:09 2012 -0700
@@ -488,17 +488,18 @@
     }
 
     /**
-     * Add a traliling file separator, if not found or strip off extra trailing
-     * file separators if any.
+     * Add a trailing file separator, if not found. Remove superfluous
+     * file separators if any. Preserve the front double file separator for
+     * UNC paths.
      *
      * @param path Path under consideration.
      * @return String Properly constructed path string.
      */
-    String addTrailingFileSep(String path) {
+    public static String addTrailingFileSep(String path) {
         String fs = System.getProperty("file.separator");
         String dblfs = fs + fs;
         int indexDblfs;
-        while ((indexDblfs = path.indexOf(dblfs)) >= 0) {
+        while ((indexDblfs = path.indexOf(dblfs, 1)) >= 0) {
             path = path.substring(0, indexDblfs) +
                 path.substring(indexDblfs + fs.length());
         }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javadoc/T4696488.java	Fri Oct 05 14:21:09 2012 -0700
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2012, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import com.sun.tools.doclets.internal.toolkit.Configuration;
+
+/**
+ * @test
+ * @bug     4696488
+ * @summary javadoc doesn't handle UNC paths for destination directory
+ * @author  Jesse Glick
+ * @run main T4696488 T4696488.java
+ */
+public class T4696488 {
+
+    public static void main(String... args) {
+        System.setProperty("file.separator", "/");
+        assertAddTrailingFileSep("/path/to/dir", "/path/to/dir/");
+        assertAddTrailingFileSep("/path/to/dir/", "/path/to/dir/");
+        assertAddTrailingFileSep("/path/to/dir//", "/path/to/dir/");
+        System.setProperty("file.separator", "\\");
+        assertAddTrailingFileSep("C:\\path\\to\\dir", "C:\\path\\to\\dir\\");
+        assertAddTrailingFileSep("C:\\path\\to\\dir\\", "C:\\path\\to\\dir\\");
+        assertAddTrailingFileSep("C:\\path\\to\\dir\\\\", "C:\\path\\to\\dir\\");
+        assertAddTrailingFileSep("\\\\server\\share\\path\\to\\dir", "\\\\server\\share\\path\\to\\dir\\");
+        assertAddTrailingFileSep("\\\\server\\share\\path\\to\\dir\\", "\\\\server\\share\\path\\to\\dir\\");
+        assertAddTrailingFileSep("\\\\server\\share\\path\\to\\dir\\\\", "\\\\server\\share\\path\\to\\dir\\");
+    }
+
+    private static void assertAddTrailingFileSep(String input, String expectedOutput) {
+        String output = Configuration.addTrailingFileSep(input);
+        if (!expectedOutput.equals(output)) {
+            throw new Error("expected " + expectedOutput + " but was " + output);
+        }
+    }
+
+}