Get a table name

Hi all,
I'm trying to get the table name of a column in this way:

ResultSet rs;
try
{
rs = ps.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData();
System.out.println(rsmd.getTableName(..));

but the getTableName( ..) method gives me an empty string. Isn't there a
way to know the table name of a specific field I'm obtaining? Thanks