title: Saving private variables on a spring @Service
body: <p>I want to save data on a spring <code>@Service</code> to be used every time the service is called.</p>
  
  <p>Is it a good idea to save it as a private class member like in the example below?</p>
  
  <pre><code>@Service
  public class MyServiceImpl implements MyService {
      private int counter;
  
      @Override
      public int increment() {
          return counter++;
      }
  }
  </code></pre>