java – Log4J 2配置监控和按位比较

/**
  * Called to determine if the configuration has changed.
  */
 @Override
 public void checkConfiguration() {
     final long current = System.currentTimeMillis();
     if (((counter.incrementAndGet() & MASK) == 0) && (current >= nextCheck)) {
         LOCK.lock();
         try {
             nextCheck = current + intervalSeconds;
             if (file.lastModified() > lastModified) {
                 lastModified = file.lastModified();
                 for (final ConfigurationListener listener : listeners) {
                     final Thread thread = new Thread(new ReconfigurationWorker(listener,reconfigurable));
                     thread.setDaemon(true);
                     thread.start();
                 }
             }
         } finally {
             LOCK.unlock();
         }
     }

其中counter是AtomicInteger字段,MASK设置为0x0f,nextCheck为long.

据我所知,此方法检查是否重新加载配置,但仅当计数器的值可被16整除并且下一个配置检查周期已过时才会这样做.

为什么这是按位和那里？

鉴于对于计数器实例,incrementAndGet是同步的,它可以被认为是“廉价”的限制机制吗？或者也许在“典型”nextCheck周期期间调用checkConfiguration的次数超过必要的次数,因此按位AND作为性能技巧(再次,限制？).