src/share/classes/java/lang/Character.java

@@ -2569,10 +2569,14 @@
      * should generally be used in preference to the constructor
      * {@link #Character(char)}, as this method is likely to yield
      * significantly better space and time performance by caching
      * frequently requested values.
      *
+     * This method will always cache values in the range '\u0000'
+     * to '\u007f'", inclusive, and may cache other values outside
+     * of this range.
+     *
      * @param  c a char value.
      * @return a <tt>Character</tt> instance representing <tt>c</tt>.
      * @since  1.5
      */
     public static Character valueOf(char c) {