一段代码，引发的思考。

最近看了一段有意思的代码，大家来看看这段有什么问题！想看看大家的想法。代码如下：

abstract static class StaticServiceFetcher extends ServiceFetcher {
private Object mCachedInstance;

@Override
public final Object getService(ContextImpl unused) {
synchronized (StaticServiceFetcher.this) {
Object service = mCachedInstance;
if (service != null) {
return service;
}
return mCachedInstance = createStaticService();
}
}

public abstract Object createStaticService();
}