import java.sql.SQLException;
import java.util.Random;
import sqlj.runtime.ExecutionContext;
import oracle.sqlj.runtime.Oracle;

/**
  Each instance of MultiThreadDemo is a thread that gives all employees
  a raise of some ammount when run.  The main program creates two such 
  instances and computes the net raise after both threads have completed.
  **/
class MultiThreadDemo extends Thread
{
  double raise;
  static Random randomizer = new Random(); 
 
  public static void main (String args[]) 
  {
    try { 
      /* if you're using a non-Oracle JDBC Driver, add a call here to
	  DriverManager.registerDriver() to register your Driver
      */

      // set the default connection to the URL, user, and password
      // specified in your connect.properties file
      Oracle.connect(MultiThreadDemo.class, "connect.properties");
      double avgStart = calcAvgSal();
      MultiThreadDemo t1 = new MultiThreadDemo(250.50);
      MultiThreadDemo t2 = new MultiThreadDemo(150.50);
      t1.start();
      t2.start();
      t1.join();
      t2.join();
      double avgEnd = calcAvgSal();
      System.out.println("average salary change: " + (avgEnd - avgStart));
    } catch (Exception e) { 
      System.err.println("Error running the example: " + e);
    }
  } 

  static double calcAvgSal() throws SQLException
  {
    double avg;
    #sql { SELECT AVG(sal) INTO :avg FROM emp };
    return avg;
  }

  MultiThreadDemo(double raise)
  {
    this.raise = raise;
  }

  public void run()
  {
    // Since all threads will be using the same default connection
    // context, each run uses an explicit execution context instance to
    // avoid conflict during execution
    try {
      delay();
      ExecutionContext execCtx = new ExecutionContext();
      #sql [execCtx] { UPDATE EMP SET sal = sal + :raise };
      int updateCount = execCtx.getUpdateCount();
      System.out.println("Gave raise of " + raise + " to " + 
			 updateCount + " employees");
    } catch (SQLException e) {
      System.err.println("error updating employees: " + e);
    }
  }

  // delay is used to introduce some randomness into the execution order
  private void delay()
  {
    try {
      sleep((long)Math.abs(randomizer.nextInt()/10000000));
    } catch (InterruptedException e) {}
  }
}