import java.sql.*;
import java.util.HashSet;  import java.io.FileInputStream;  import java.util.Properties;
class JdbcConnectionOverflow {
public static void main (String args [])
throws Exception {
  DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
  Properties props = new Properties();
  props.load(new FileInputStream("conn.props"));
  String url = props.getProperty("url");
  Connection conn;  Statement stmt;  ResultSet rset;
  int i = 0;
  HashSet<Connection> s = new HashSet<Connection>();
  while (true) {
    try { Thread.sleep(200);  i++;  System.out.println(i);
      conn = DriverManager.getConnection(url, props);
      s.add(conn);
      stmt = conn.createStatement();
      rset = stmt.executeQuery("select * from qwertz");
    } catch (SQLException e) { e.printStackTrace(); }
    catch (InterruptedException ex) { Thread.currentThread().interrupt(); }
}}}
/* ADMIN only:
select username, count(*) from V$SESSION group by username; */