public boolean isField() {
      switch (this) {
        case METHOD_HANDLE_TYPE_STATIC_PUT:
        case METHOD_HANDLE_TYPE_STATIC_GET:
        case METHOD_HANDLE_TYPE_INSTANCE_PUT:
        case METHOD_HANDLE_TYPE_INSTANCE_GET:
          return true;
        default:
          return false;
      }
    }
A method handle type code:
https://source.android.com/devices/tech/dalvik/dex-format#method-handle-type-codes
android/android_framework/dex-maker/src/main/java/com/android/dex/MethodHandle.java