code: public static FieldNode findField(ClassNode classNode, String name) {
          Validate.notNull(classNode);
          Validate.notNull(name);
          Validate.notEmpty(name);
          return classNode.fields.stream()
                  .filter(x -> name.equals(x.name))
                  .findAny().orElse(null);
      }
docs: Find field within a class by its name.
  @param classNode class to search
  @param name name to search for
  @return found field (or {@code null} if not found)
  @throws NullPointerException if any argument is {@code null}
  @throws IllegalArgumentException if {@code name} is empty