Java实例：超类型和子类型似乎相等？如何准确测试Type？

Question

如果实例完全属于给定类型，我需要测试。但是，如果子类型被测试为超类型，则似乎instanceof也返回true（情况3）。我以前从来不知道这一点，我很惊讶。我在这里做错了吗？我如何准确测试给定类型？

//..

class DataSourceEmailAttachment extends EmailAttachment

//...

EmailAttachment emailAttachment = new EmailAttachment();
DataSourceEmailAttachment emailAttachmentDS = new DataSourceEmailAttachment();

    if (emailAttachment instanceof EmailAttachment){
        System.out.println(" 1");
    }
    if (emailAttachment instanceof DataSourceEmailAttachment){
        System.out.println(" 2");
    }

    if (emailAttachmentDS instanceof EmailAttachment){
        System.out.println(" 3 ");
    }
    if (emailAttachmentDS instanceof DataSourceEmailAttachment){
        System.out.println(" 4");
    }

结果：

 1
 3 
 4

我想避免案例3 ，我只想要“完全匹配”（案例1和4）我该如何测试它们？

Answer 1

if( emailAttachment.getClass().equals(EmailAttachment.class) )