code: public boolean isModified()
    {
      synchronized (this) {
        if (_isChecking || _isModified) {
          return _isModified;
        }
  
        _isChecking = true;
      }
  
      try {
        long now;
  
        now = CurrentTime.currentTime();
  
        if (now < _lastCheckTime + _checkInterval)
          return _isModified;
  
        _lastCheckTime = now;
  
        for (int i = _dependencyList.size() - 1; i >= 0; i--) {
          Dependency dependency = _dependencyList.get(i);
  
          if (dependency.isModified()) {
            dependency.logModified(log());
  
            _isModified = true;
  
            return _isModified;
          }
        }
  
        // _isModified = false;
  
        return _isModified;
      } finally {
        _isChecking = false;
      }
    }
docs: Returns true if the underlying dependencies have changed.