--- old/src/java.base/share/classes/java/nio/file/Files.java	2018-09-18 19:47:11.848369329 -0700
+++ new/src/java.base/share/classes/java/nio/file/Files.java	2018-09-18 19:47:10.958274145 -0700
@@ -91,6 +91,9 @@
  */
 
 public final class Files {
+    // buffer size used for reading and writing
+    static final int BUFFER_SIZE = 8192;
+
     private Files() { }
 
     /**
@@ -1530,6 +1533,53 @@
         return provider(path).isSameFile(path, path2);
     }
 
+
+    /**
+     * Finds and returns the index of the first mismatched byte in the content
+     * of two files, or returns -1 if the files are equal.
+     *
+     * <p> Two files are considered equal if they satisfy one of the following
+     * conditions:
+     * <ul>
+     *   <li> {@link #isSameFile(Path, Path) isSameFile(path, path2)} returns true,</li>
+     *   <li> the files are the same length, and every byte of the first file equals
+     *   the corresponding byte of the second file.</li>
+     * </ul>
+     *
+     * <p>Otherwise, there is a mismatch between the two files. This method returns
+     * a mismatch value, computed as follows:
+     * <ul>
+     *   <li> the index of the first position in the files at which mismatched bytes
+     *   are found, or</li>
+     *   <li> the length of the smaller file, if the files are of unequal length,
+     *   and if every byte of the smaller file equals the corresponding byte of
+     *   the larger file.</li>
+     * </ul>
+     *
+     * <p>This method may not be atomic with respect to other file system operations.
+     *
+     * @param   path
+     *          the path to the first file
+     * @param   path2
+     *          the path to the second file
+     *
+     * @return  the index of the first mismatch between the two files, or {@code -1}
+     *          if there is no mismatch.
+     *
+     * @throws  IOException
+     *          if an I/O error occurs, or path or path2 does not exist unless
+     *          they are the same object
+     * @throws  SecurityException
+     *          In the case of the default provider, and a security manager is
+     *          installed, the {@link SecurityManager#checkRead(String) checkRead}
+     *          method is invoked to check read access to both files.
+     * @since 12
+     *
+     */
+    public static long mismatch(Path path, Path path2) throws IOException {
+        return FilesMismatch.mismatch(path, path2);
+    }
+
     /**
      * Tells whether or not a file is considered <em>hidden</em>. The exact
      * definition of hidden is platform or provider dependent. On UNIX for
@@ -2802,8 +2852,6 @@
 
     // -- Utility methods for simple usages --
 
-    // buffer size used for reading and writing
-    private static final int BUFFER_SIZE = 8192;
 
     /**
      * Opens a file for reading, returning a {@code BufferedReader} that may be