Review

Map.get() and Map.put() are called with different (types of) objects as key. There is another Map, for which the accidentially used key is the correct key.

• missing/condition/value_or_state

org/apache/lucene/search/FieldCacheImpl.java

get(IndexReader, Object)

class FieldCacheImpl.Cache {
    public Object get(IndexReader reader, Object key) throws IOException {
      Map innerCache;
      Object value;
      synchronized (readerCache) {
        innerCache = (Map) readerCache.get(reader);
        if (innerCache == null) {
          innerCache = new HashMap();
          readerCache.put(reader, innerCache);
          value = null;
        } else {
          value = innerCache.get(key);
        }
        if (value == null) {
          value = new CreationPlaceholder();
          innerCache.put(reader, value);
        }
      }
      if (value instanceof CreationPlaceholder) {
        synchronized (value) {
          CreationPlaceholder progress = (CreationPlaceholder) value;
          if (progress.value == null) {
            progress.value = createValue(reader, key);
            synchronized (readerCache) {
              innerCache.put(key, progress.value);
            }
          }
          return progress.value;
        }
      }
      return value;
    }

}

abstract class UseKeyForMapRetrieve {
  void get(Map innerCache, Object key) throws IOException {
    Object value;
    if (innerCache == null) {
      innerCache = new HashMap();
      value = null;
    } else {
      value = innerCache.get(key);
    }
    if (value == null) {
      value = new CreationPlaceholder();
      innerCache.put(key, value);
    }
  }
  
  static final class CreationPlaceholder {
    Object value;
  }
}