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

*** 89,98 ****
--- 89,101 ----
   *
   * @since 1.7
   */
  
  public final class Files {
+     // buffer size used for reading and writing
+     static final int BUFFER_SIZE = 8192;
+ 
      private Files() { }
  
      /**
       * Returns the {@code FileSystemProvider} to delegate to.
       */
*** 1528,1537 ****
--- 1531,1587 ----
       */
      public static boolean isSameFile(Path path, Path path2) throws IOException {
          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
       * example a file is considered to be hidden if its name begins with a
       * period character ('.'). On Windows a file is considered hidden if it
*** 2800,2811 ****
      }
  
  
      // -- 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
       * used to read text from the file in an efficient manner. Bytes from the
       * file are decoded into characters using the specified charset. Reading
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