Retrieve mean and standard deviation from Cassandra, writing values to a file

GetMeanSD.java

package com.streamsets.example.cassandra;

import com.datastax.driver.core.BoundStatement;
import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.PreparedStatement;
import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;

import java.io.PrintWriter;
import java.util.Date;

public class GetMeanSD {
  private static final long timeRangeMillis = 3600L * 1000L;
  private static final long sleepMillis = 60L * 1000L;
  private static final int sensorId = 1;
  private static final String resourceDir = "/home/pi/streamsets-datacollector-1.4.0.0/resources/";
  private static final String cassandraHost = "192.168.69.141";
  private static final String keyspace = "mykeyspace";

  public static void main(String[] args) throws Exception {
    Cluster cluster = Cluster.builder().addContactPoint(cassandraHost).build();
    Session session = cluster.connect(keyspace);

    // Use a PreparedStatement since we'll be issuing the same query many times
    PreparedStatement statement = session.prepare("SELECT COUNT(*), AVG(temperature), STDEV(temperature) " +
        "FROM sensor_readings " +
        "WHERE sensor_id = ? " +
        "AND TIME > ?");
    BoundStatement boundStatement = new BoundStatement(statement);

    while (true) {
      long startMillis = System.currentTimeMillis() - timeRangeMillis;
      ResultSet results = session.execute(boundStatement.bind(sensorId, new Date(startMillis)));
      Row row = results.one();

      long count = row.getLong("count");
      double avg = row.getDouble("system.avg(temperature)"),
             sd  = row.getDouble("mykeyspace.stdev(temperature)");

      System.out.println("COUNT: "+count+", AVG: "+avg+", SD: "+sd);

      try (PrintWriter writer = new PrintWriter(resourceDir + "mean.txt", "UTF-8")) {
        writer.format("%g", avg);
      }
      try (PrintWriter writer = new PrintWriter(resourceDir + "sd.txt", "UTF-8")) {
        writer.format("%g", sd);
      }

      Thread.sleep(sleepMillis);
    }
  }
}