One question about connection parameter stringtype

Hi,

When i run my program which use pgjdbc,a error happened.

my program looks like the following：

PreparedStatement pstmt = con.prepareStatement("select 1=？");
pstmt.setString(1, null);
pstmt.executeUpdate();

error message:
operator does not exist: integer = character varying

The error's resean is just as the error message said, and i known this can be avoided
by set stringtype=unspecified in url. But i still have two question。

1）when stringtype is setted to be "unspecified",is there any bad think would happen?

2)If the answer of 1）is "nothing",why pgjdbc not setting the default value of stringtype to "unspecified"

kavi314