How to find out if a Java ResultSet obtained is empty?

Question

Class.forName("org.sqlite.JDBC");
Connection conn =
    DriverManager.getConnection("jdbc:sqlite:userdata.db");
Statement stat = conn.createStatement();

ResultSet rs = stat.executeQuery("SELECT * from table WHERE is_query_processed = 0;");

int rowcount = rs.getRow(); 
System.out.println("Row count = "+rowcount); // output 1

rs.first(); // This statement generates an exception

Why is it so?

Answer 1

The pattern I normally use is as follows:

boolean empty = true;
while( rs.next() ) {
    // ResultSet processing here
    empty = false;
}

if( empty ) {
    // Empty result set
}

Answer 2

Here's a simple method to do it:

public static boolean isResultSetEmpty(ResultSet resultSet) {
    return !resultSet.first();
}

Caveats

This moves the cursor to the beginning. But if you just want to test whether it's empty, you probably haven't done anything with it yet anyways.

Alternatively

Use the first() method immediately, before doing any processing. ResultSet rs = stat.executeQuery("SELECT * from table WHERE is_query_processed = 0;");

if(rs.first()) {
    // there's stuff to do
} else {
    // rs was empty
}

References

ResultSet (Java Platform SE 6)