@Nullable
  private static InternalInstalledJdk readJdk(IonReader reader) {
    IonType ionType = reader.next();
    assertFieldName(reader, "jdk");
    if (ionType == IonType.NULL || ionType == null) {
      return null;
    }

    reader.stepIn();
    File javaHome = readFile(reader, "javaHome");
    String versionString = readString(reader, "javaVersion");
    JavaVersion javaVersion = versionString == null ? null : JavaVersion.valueOf(versionString);
    InternalInstalledJdk jdk = new InternalInstalledJdk(javaHome, javaVersion);
    reader.stepOut();
    return jdk;
  }
@Nullable
  private static InternalInstalledJdk readJdk(IonReader reader)