synchronized void setDeadLetters(final DeadLetters deadLetters) {
    if (deadLetters != null && this.deadLetters != null) {
      deadLetters.stop();
      throw new IllegalStateException("Dead letters already exists.");
    }

    this.deadLetters = deadLetters;
  }
synchronized void setDeadLetters ( final DeadLetters deadLetters ) { if ( deadLetters != null && this . deadLetters != null ) { deadLetters . stop ( ) ; throw new IllegalStateException ( "Dead letters already exists." ) ; } this . deadLetters = deadLetters ; }
Sets the {@code DeadLetters} as the default for this {@code World}. (INTERNAL ONLY)
@param deadLetters the {@code DeadLetters} to register as the default