Java ResultSet how to check if there are any results

That's correct, initially the ResultSet's cursor is pointing to before the first row, if the first call to next() returns false then there was no data in the ResultSet.

If you use this method, you may have to call beforeFirst() immediately after to reset it, since it has positioned itself past the first row now.

It should be noted however, that Seifer's answer below is a more elegant solution to this question.

you could always do the next up front, and just do a post loop check

if (!resultSet.next() ) {
    System.out.println("no data");
} else {

    do {
     //statement(s)
    } while (resultSet.next());
}

You would usually do something like this:

while ( resultSet.next() ) { 
   // Read the next item
   resultSet.getString("columnName");
}

If you want to report an empty set, add a variable counting the items read. If you only need to read a single item, then your code is adequate.

That would work if you want to see if there are any rows in the result set yes.

Note that next() always moves to the next row, so if you are planning on doing any reading from the result set you need to take that into account.

Usual usage with ResultSet (when simply reading) is:

while (resultSet.next())
{
   ... read from the row here ...
}

Which obviously won't work correctly if you invoked next() once already to check if the result set was empty, so watch out for that. Although there are methods for "backing up", they are not supported for all types of result sets.

Why not use rs.getRow()?

int getRow()
           throws SQLException
Retrieves the current row number. The first row is number 1, the second number 2, and so on.
Note:Support for the getRow method is optional for ResultSets with a result set type of TYPE_FORWARD_ONLY

Returns:
the current row number; 0 if there is no current row
Throws:
SQLException - if a database access error occurs or this method is called on a closed result set
SQLFeatureNotSupportedException - if the JDBC driver does not support this method
Since:
1.2

For me check "if (rs.getRow() != 0)" seems to work just fine.

The best thing for to do is to check the first row so that when you intend to get the data you can avoid the mistake of skipping a row. Something like: if (!resultSet.first() ) { System.out.println("no data"); }

if (resultSet==null ) {
    System.out.println("no data");
}

A word of caution,

if you are using the org.springframework.jdbc.core.RowMapper be very careful how you are checking that your ResultSet is empty since the following holds true for the mapRow method:

This method should not call next() on the ResultSet; it is only supposed to map values of the current row. <- from the documentation

In this situation, your check can become something along the lines of

resultSet.beforeFirst();
if (!resultSet.next() ) {
    System.out.println("no data");
}