--- old/src/java.base/share/classes/java/nio/file/Path.java	2018-02-15 08:44:12.000000000 -0800
+++ new/src/java.base/share/classes/java/nio/file/Path.java	2018-02-15 08:44:12.000000000 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2018, 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
@@ -45,10 +45,13 @@
  * A {@code Path} is considered to be an <i>empty path</i> if it consists
  * solely of one name element that is empty. Accessing a file using an
  * <i>empty path</i> is equivalent to accessing the default directory of the
- * file system. {@code Path} defines the {@link #getFileName() getFileName},
- * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
- * subpath} methods to access the path components or a subsequence of its name
- * elements.
+ * file system. The <em>extension</em> of a {@code Path} is defined to be the
+ * portion of the path after but not including the last dot ({@code '.'}) and
+ * is part of the name element farthest from the root. {@code Path} defines the
+ * {@link #getFileName() getFileName}, {@link #getParent getParent},
+ * {@link #getRoot getRoot}, {@link #getExtension getExtension}, and
+ * {@link #subpath subpath} methods to access the path components or a
+ * subsequence of its name elements.
  *
  * <p> In addition to accessing the components of a path, a {@code Path} also
  * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
@@ -161,6 +164,36 @@
     Path getParent();
 
     /**
+     * Returns the extension of this {@code Path} as a {@code String}.
+     * The extension is that portion of the path after the last dot
+     * ({@code '.'}).  If this path is empty, does not contain a dot, ends
+     * with a dot, or has a {@link FileSystem#getSeparator() name-separator}
+     * after the last dot, then this method returns an empty {@code String}.
+     *
+     * @implSpec
+     * For the cases where a non-empty string would be returned, the default
+     * implementation is equivalent for this path to:
+     * <pre>{@code
+     *     toString().substring(toString().lastIndexOf(".") + 1);
+     * }</pre>
+     *
+     * @return  the extension of this path or an empty {@code String}
+     *
+     * @since 11
+     */
+    default String getExtension() {
+        String path = toString();
+
+        int lastDot = path.lastIndexOf(".");
+        if (lastDot == -1 || lastDot == path.length() - 1 ||
+            path.indexOf(getFileSystem().getSeparator(), lastDot + 1) != -1) {
+            return "";
+        }
+
+        return path.substring(lastDot + 1);
+    }
+
+    /**
      * Returns the number of name elements in the path.
      *
      * @return  the number of elements in the path, or {@code 0} if this path