It wasn't clear on first reading that constantValue() and
constantValueExpression() are two representions of the same value.
Suggested text for the returns clause is as follows:

constantValue
   * @returns an object containing the value of a constant field. (For a
   * string representation, use {@link #constantValueExpression}.)
   * The value is automatically wrapped in an object if it has a
   * primitive type. If the field is not constant, returns null.

constantValueExpression
   * @returns a string containing the value of a constant field. (For an
   * object representation, use {@link #constantValue}.)
   * The text of the string is a Java language expression whose
   * value is the value of the constant. The expression uses no
   * identifiers other than primitive literals. If the field is
   * not constant, returns null.

(This request was originally part of bug 4947357)