Java Instance of: Supertypes and Subtypes seem to be equal? How to test exactly for Type?
- by jens
I need to test, if an instance is exactly of a given type. But it seems that instanceof returns true also if the subtype is tested for the supertype (case 3). I never knew this before and I am quite surprised. Am I doing something wrong here? How do I exactly test for a given type?
//..
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");
}
RESULT:
1
3
4
I want to avoid case 3, I only want "exact matches" (case 1 and 4) how do I test for them?
