Java sql delete statement works with =, but doesn't work with in ()?

Question

In Java DAO object following statement works:

String sqlDelete =  "delete from table where id = ?";  //Argument is 1

This deletes exactly one row.

However, when I change it to:

"delete from table where id in (?)";//Argument is 1,2

0 rows deleted. No errors, no exceptions. When I run the statement in SQL, it works correctly.

Any ideas why equals operator works, but in operator doesn't?