code: public String getMethodDescriptor(ExecutableType method) {
      StringBuilder sb = new StringBuilder("(");
      for (TypeMirror t : method.getParameterTypes()) {
        sb.append(getSignatureName(t));
      }
      sb.append(")");
      sb.append(getSignatureName(method.getReturnType()));
      return sb.toString();
    }
docs: Returns the descriptor of a constructor or method (JLS 4.3.3).