jdbc and processing output using Jakarta Commons Math - apache

Question

Using jdbc I am querying my database of ambulance response times. My goal is to take the output and process it into statistics using Jakarta Commons Math library. So far I am successful in querying my database and outputting the response times to the console. My next step is to process this output statistically, such as mean, medians, mode, etc. This is where I am stuck. Shown below is my code.
package javaDatabase;
import java.sql.*;
import org.apache.commons.math3.stat.StatUtils;
public class javaConnect3
{
public static void main(String[] args)
{
Connection conn = null;
Statement stmt = null;
try
{
conn = DriverManager
.getConnection("jdbc:sqlserver://myServerAddress;database=myDatabase;integratedsecurity=false;user=myUser;password=myPassword");
stmt = conn.createStatement();
String strSelect = "SELECT M_SecondsAtStatus FROM MManpower WHERE M_tTime > 'august 25, 2014' AND M_Code = 'USAR'";
ResultSet rset = stmt.executeQuery(strSelect);
while (rset.next())
{
int values = rset.getInt("M_SecondsAtStatus");
System.out.println(values);
}
// I am hoping to derive useful statistics from my database, such as the following.
// this uses Jakarta Commons Math
// System.out.println("min: " + StatUtils.min(values));
// System.out.println("max: " + StatUtils.max(values));
// System.out.println("mean: " + StatUtils.mean(values));
// System.out.println("product: " + StatUtils.product(values));
// System.out.println("sum: " + StatUtils.sum(values));
// System.out.println("variance: " + StatUtils.variance(values));
} catch (SQLException ex)
{
ex.printStackTrace();
} finally
{
try
{
if (stmt != null)
stmt.close();
if (conn != null)
conn.close();
} catch (SQLException ex)
{
ex.printStackTrace();
}
}
}
}
An error message pops up in Eclipse and the variable "values" is red underlined; "values cannot be resolved to a variable".
I am not sure how to get this to work. I don't understand how to output my ambulance response times from the database into something Apache Commons math will understand.
How can I get Apache Commons math to take the output from my database and generate a statistical result?

Answer 1

You need something like this:
List<Double> values = new ArrayList<Double>();
while (rset.next()) {
values.add(rset.getInt("M_SecondsAtStatus"));
}
double mean = StatsUtils.mean(values.toArray(new Double [](values.size()));
It's likely that you could query the database for statistics. The name of the method depends on your database:
SELECT avg(M_SecondsAtStatus)
FROM MManpower
WHERE M_tTime > 'august 25, 2014'
AND M_Code = 'USAR'
I'd say the second one is more efficient, because you don't have to transfer all those values to the Java JVM to do the same calculation that the database can do for you.

Answer 2

Another alternative is to use a DescriptiveStatistics object to collect all the data and then use it to compute the summary statistics you need. Using it alleviates the need for doing all explicit type casting and conversion:
DescriptiveStatistics ds = new DescriptiveStatistics();
while(rset.next()) {
int observation = rset.getInt("M_SecondsAtStatus");
ds.addValue(observation);
}
System.out.println("min: " + ds.getMin());
System.out.println("max: " + ds.getMax());
...