Re: Amazing: Vector can have elements of different types!!!

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 15 Sep 2006 13:44:45 GMT

Message-ID:

<h7yOg.11910$bM.384@newsread4.news.pas.earthlink.net>

Shawn wrote:

Hi,

I just realized/found that in Java, Vector can have elements with
different types. I guess other collections are the same. See my code
below. I don't know Generics from Java 5.0. But I am really amazed that
heterogenous types of data can be put in the same place(Vector).

I have a couple questions:
(1)Is that common that people utilize this feature (putting different
types of data in one place)?

I don't usually mix classes whose only common superclass is Object. More
often, all the elements implement or extend a specific interface or
class other than Object.

The new generics features allow tagging of a Vector (or other java.util
collection) with the intended type of its contents.

(2)Is there a way to find out what type of each element belongs to? (say
I forgot 1st element is Person, 2nd element is String, etc)

if(a instanceof Person)...

Have you read a Java textbook? If not, I suggest doing so. You seem to
be discovering the basics of how to use Java by a mix of experimentation
and asking how to do things in this newsgroup, which is not very
efficient and may leave serious gaps in your Java skills.

Patricia