318      * sequence.
 319      * <p>
 320      * The characters of the {@code CharSequence} argument are appended,
 321      * in order, increasing the length of this sequence by the length of the
 322      * argument.
 323      *
 324      * <p>The result of this method is exactly the same as if it were an
 325      * invocation of this.append(s, 0, s.length());
 326      *
 327      * <p>This method synchronizes on {@code this}, the destination
 328      * object, but does not synchronize on the source ({@code s}).
 329      *
 330      * <p>If {@code s} is {@code null}, then the four characters
 331      * {@code "null"} are appended.
 332      *
 333      * @param   s the {@code CharSequence} to append.
 334      * @return  a reference to this object.
 335      * @since 1.5
 336      */
 337     @Override
 338     public StringBuffer append(CharSequence s) {
 339         // Note, synchronization achieved via invocations of other StringBuffer methods after
 340         // narrowing of s to specific type
 341         // Ditto for toStringCache clearing
 342         super.append(s);
 343         return this;
 344     }
 345 
 346     /**
 347      * @throws IndexOutOfBoundsException {@inheritDoc}
 348      * @since      1.5
 349      */
 350     @Override
 351     public synchronized StringBuffer append(CharSequence s, int start, int end)
 352     {
 353         toStringCache = null;
 354         super.append(s, start, end);
 355         return this;
 356     }
 357 
 358     @Override
 359     public synchronized StringBuffer append(char[] str) {
 360         toStringCache = null;
 361         super.append(str);

 318      * sequence.
 319      * <p>
 320      * The characters of the {@code CharSequence} argument are appended,
 321      * in order, increasing the length of this sequence by the length of the
 322      * argument.
 323      *
 324      * <p>The result of this method is exactly the same as if it were an
 325      * invocation of this.append(s, 0, s.length());
 326      *
 327      * <p>This method synchronizes on {@code this}, the destination
 328      * object, but does not synchronize on the source ({@code s}).
 329      *
 330      * <p>If {@code s} is {@code null}, then the four characters
 331      * {@code "null"} are appended.
 332      *
 333      * @param   s the {@code CharSequence} to append.
 334      * @return  a reference to this object.
 335      * @since 1.5
 336      */
 337     @Override
 338     public synchronized StringBuffer append(CharSequence s) {
 339         toStringCache = null;


 340         super.append(s);
 341         return this;
 342     }
 343 
 344     /**
 345      * @throws IndexOutOfBoundsException {@inheritDoc}
 346      * @since      1.5
 347      */
 348     @Override
 349     public synchronized StringBuffer append(CharSequence s, int start, int end)
 350     {
 351         toStringCache = null;
 352         super.append(s, start, end);
 353         return this;
 354     }
 355 
 356     @Override
 357     public synchronized StringBuffer append(char[] str) {
 358         toStringCache = null;
 359         super.append(str);