code: public static XField getExactXField(@SlashedClassName String className, String name, String signature, boolean isStatic) {
          FieldDescriptor fieldDesc = DescriptorFactory.instance().getFieldDescriptor(ClassName.toSlashedClassName(className),
                  name, signature, isStatic);
          return getExactXField(fieldDesc);
      }
docs: Get an XField object exactly matching given class, name, and signature.
  May return an unresolved object (if the class can't be found, or does not
  directly declare named field).
  
  @param className
  name of class containing the field
  @param name
  name of field
  @param signature
  field signature
  @param isStatic
  field access flags
  @return XField exactly matching class name, field name, and field
  signature