Upto java  1.4 you can only hold reference types  in the
Collection/Container classes  so you are stuck with
either using arrays or using the wrapper classes for
the primitives. This has been remedied somewhat in
Java 1.5 with the introduction of generics. The syntax
will be familiar if you know templates in C++.

ie.

Stack<int> col = new Stack<int>();
col.add(2);

note that this is not technically equivalent to it's
C++ counterpart in that it is not compiled to a
different type of Stack rather it is more like an
instruction for the compiler to disallow entries to
the above Stack that are not Integers. Note I said
Integers and not int's because the second line above
is "translated" into col.add(new Integer(2));.

For a more complete description of Generics in java go
to:

http://www.ociweb.com/jnb/jnbJul2003.html