Why Tomcat's LifyCycleSupport.java use array to store listeners instead of any advanced containers(ArrayList)?

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Im recently going through tomcat's source code, I found that in the LifecycleSupport.java class, it stores Listeners by simple arrays,

private LifecycleListener listeners[] = new LifecycleListener[0];

so the add() method has to create a new array to replace the old one:

public void addLifecycleListener(LifecycleListener listener) {
   82   
   83         synchronized (listenersLock) {
   84             LifecycleListener results[] =
   85               new LifecycleListener[listeners.length + 1];
   86             for (int i = 0; i < listeners.length; i++)
   87                 results[i] = listeners[i];
   88             results[listeners.length] = listener;
   89             listeners = results;
   90         }
   91   
   92       }

I wonder whats the purpose to use array instead of advanced java containers like ArrayList, since its much more convenient to perform add/remove action?

Thanks

asked 34 secs ago

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Why Tomcat's LifyCycleSupport.java use array to store listeners instead of any advanced containers(ArrayList)?