: Supertypes and Subtypes seem to be equal?的Java实例如何准确测试类型？

Question

我需要测试一个实例是否完全属于给定类型。但是，如果针对父类(super class)型测试子类型(情况 3)，instanceof 似乎也会返回 true。我以前从来不知道这一点，我很惊讶。我在这里做错了什么吗？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

我想避免情况 3，我只想“完全匹配”(情况 1 和 4)，我该如何测试它们？

Answer 1

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