docs: public Class<?> getParameterType() {
          if (this.parameterType == null) {
              if (this.parameterIndex < 0) {
                  this.parameterType = (this.method != null ? this.method.getReturnType() : null);
              } else {
                  this.parameterType = (this.method != null ? this.method.getParameterTypes()[this.parameterIndex]
                          : this.constructor.getParameterTypes()[this.parameterIndex]);
              }
          }
          return this.parameterType;
      }