import java.util.*;
public class Interval {
  private Date startDate_; // unique
  private Date endDate_; // unique
  public Interval() {
    startDate_ = new Date();
    endDate_ = new Date();
  }
  public synchronized void setStart(int date){
    startDate_.setTime(date);
  }
  public synchronized void setEnd(int date){
    endDate_.setTime(date);
  }
  public synchronized long duration() {
    return endDate_.getTime() - startDate_.getTime();
  }
}

// class date
// getTime 
// public long getTime() 
// Returns: 
// the number of milliseconds since January 1, 
// 1970, 00:00:00 GMT represented by this date.