Java对象实例链式调用多个方法时空值(null)判断方法总结

1､一般通常的判断方法

private boolean sourceWebsite(Registration registration) {
    Application application = registration.getApplication();
    if (application == null) {
        return true;
    }
    Metadata metadata = application.getMetadata();
    if (metadata == null) {
        return true;
    }
    Boolean source = metadata.getSource();
    if (source == null) {
        return true;
    }
    return !source;
}

2､使用java.util.Optional判断方法

private boolean sourceWebsite(Registration registration) {
    return Optional.of(registration)
        .map(Registration::getApplication)
        .map(Application::getMetadata)
        .map(Metadata::getSource)
        .map(source -> !source)
        .orElse(Boolean.TRUE);
}

3､使用||(或)运算符判断

private boolean sourceWebsite(Registration registration) {
      Application application;
      Metadata metadata;
      Boolean source;
      return (application = registration.getApplication()) == null 
      ||     (metadata = application.getMetadata()) == null
      ||     (source = metadata.getSource()) == null
      ||    !source;
 }

4､使用try-catch块判断

private boolean sourceWebsite(Registration registration) {
    try {
        return !registration.getApplication().getMetadata().getSource();
    }
    catch (NullPointerException e) {
        return true;
    }
}