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public enum Day {
  MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
}

public final class Diary {
  private static final ThreadLocal<Day> days = 
    new ThreadLocal<Day>() {
      // Initialize to Monday 
      protected Day initialValue() {
        return Day.MONDAY;
      }
    };

  private static Day currentDay() {
    return days.get();
  }

  public static void setDay(Day newDay) {
    days.set(newDay);
  }
    
  // Performs some thread-specific task
  public void threadSpecificTask() {
    // Do task ...
  }
}

public final class DiaryPool {
  final int NoOfThreads = 2; // Maximum number of threads allowed in pool
  final Executor exec;
  final Diary diary;

  DiaryPool() {
    exec = (Executor) Executors.newFixedThreadPool(NoOfThreads);
    diary = new Diary();
  }

  public void doSomething1() {
    exec.execute(new Runnable() {
      public void run() {
        Diary.setDay(Day.FRIDAY);
        diary.threadSpecificTask();
      }
    });
  } 

  public void doSomething2() {
    exec.execute(new Runnable() {
      public void run() {
        diary.threadSpecificTask();
      }
    });
  }

  public static void main(String[] args) {
    DiaryPool dp = new DiaryPool();
    dp.doSomething1(); // Thread 1, requires current day as Friday
    dp.doSomething2(); // Thread 2, requires current day as Monday
    dp.doSomething2(); // Thread 3, requires current day as Monday
  } 
}