How to get the number of rows in a ResultSet

Question

Hello,
I'm an intern and I'm trying to get the number of rows from result set in oracle using rs.last() and rs.beforeFirst() methods
but I got an error. Could Below is my sample code:
import java.sql.*;
public class SarueckConnect {
public static void main(String[] args) {
Connection con = null;
Statement stmt = null;
ResultSet re = null;
String[] ParamArray;
ParamArray = new String[24];
//Properties logon;
try {
Class.forName("oracle.jdbc.driver.OracleDriver"); //Loading the Oracle Driver.
con = DriverManager.getConnection
("jdbc:oracle:thin:@258.8.159.215:1521:test_DB","data","data"); //making the connection DB.
stmt = con.createStatement ();// Sending a query string to the database
//stmt.executeUpdate("UPDATE test_table set steuk = 6 WHERE steuk = 5");
ResultSet rs = stmt.executeQuery("SELECT mandt,kokrs,werks,arbpl,aufnr,vornr,ile01,"+
"lsa01,ism01,ile02,lsa02,ism02,ile03,lsa03,ism03,ile04,lsa04,ism04,steuk,matnr,budat,"+
"kostl,pernr,rueckid FROM test_table where steuk =6");
//Print the result out.
rs.last(); //This is the line which gives an error.
int rows = rs.getRow();
rs.beforeFirst();// I presume this is wrong to.
ParamArray = new String[24*rows];
int counter=0;
while (rs.next()) {
for (int i = 1; i <= 24; i++){
ParamArray[i-1+(counter*24)] = rs.getString(i);
System.out.print(rs.getString(i) + '\t');
System.out.println();
counter++;
} catch(Exception e) {
e.printStackTrace();
} finally {
try
if(stmt != null) stmt.close();
if(con != null) con.close();
} catch (Exception exception) {
exception.printStackTrace();
TryBapi sap = new TryBapi(ParamArray);
}When I run the code I do have the following ERROR Message:
java.sql.SQLException: Invalid operation for forward only resultset : last
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:179)
at oracle.jdbc.driver.BaseResultSet.last(BaseResultSet.java:91)
at SarueckConnect.main(SarueckConnect.java:28)Please could any body Help me out here to figure out how to correct this?
Any Help would be highly apprecited.

Answer 1

make your result set scrollable...Not such a good idea. With Oracle, the JDBC driver will read and cache all the ResultSet in memory (with other DBMSs/drivers the behavior will probably be different, but you will still have some unnecessary overhead).
You can do the caching yourself if you think it's worth it. If the piece of code you posted is why you need this for, then use a List or Vector and you won't need to know the size upfront.
Alin,
The jTDS Project.