162         }
 163 
 164         void reset() {
 165             AppContext.getAppContext().remove(this);
 166         }
 167 
 168         abstract T getInstance();
 169     }
 170 
 171     static class RecyclableSingletonFromDefaultConstructor<T> extends RecyclableSingleton<T> {
 172         private final Class<T> clazz;
 173 
 174         RecyclableSingletonFromDefaultConstructor(final Class<T> clazz) {
 175             this.clazz = clazz;
 176         }
 177 
 178         @Override
 179         T getInstance() {
 180             try {
 181                 ReflectUtil.checkPackageAccess(clazz);
 182                 return clazz.newInstance();
 183             } catch (InstantiationException | IllegalAccessException ignored) {
 184             }
 185             return null;
 186         }
 187     }
 188 
 189     abstract static class LazyKeyedSingleton<K, V> {
 190         private Map<K, V> refs;
 191 
 192         V get(final K key) {
 193             if (refs == null) refs = new HashMap<>();
 194 
 195             final V cachedValue = refs.get(key);
 196             if (cachedValue != null) return cachedValue;
 197 
 198             final V value = getInstance(key);
 199             refs.put(key, value);
 200             return value;
 201         }
 202 
 203         protected abstract V getInstance(K key);

 162         }
 163 
 164         void reset() {
 165             AppContext.getAppContext().remove(this);
 166         }
 167 
 168         abstract T getInstance();
 169     }
 170 
 171     static class RecyclableSingletonFromDefaultConstructor<T> extends RecyclableSingleton<T> {
 172         private final Class<T> clazz;
 173 
 174         RecyclableSingletonFromDefaultConstructor(final Class<T> clazz) {
 175             this.clazz = clazz;
 176         }
 177 
 178         @Override
 179         T getInstance() {
 180             try {
 181                 ReflectUtil.checkPackageAccess(clazz);
 182                 return clazz.getDeclaredConstructor().newInstance();
 183             } catch (ReflectiveOperationException ignored) {
 184             }
 185             return null;
 186         }
 187     }
 188 
 189     abstract static class LazyKeyedSingleton<K, V> {
 190         private Map<K, V> refs;
 191 
 192         V get(final K key) {
 193             if (refs == null) refs = new HashMap<>();
 194 
 195             final V cachedValue = refs.get(key);
 196             if (cachedValue != null) return cachedValue;
 197 
 198             final V value = getInstance(key);
 199             refs.put(key, value);
 200             return value;
 201         }
 202 
 203         protected abstract V getInstance(K key);