1 // Protocol Buffers - Google's data interchange format
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30 
31 package com.google.protobuf.nano;
32 
33 import java.util.HashMap;
34 import java.util.Map;
35 
36 /**
37  * Utility class for maps support.
38  */
39 public final class MapFactories {
40   public static interface MapFactory {
forMap(Map<K, V> oldMap)41     <K, V> Map<K, V> forMap(Map<K, V> oldMap);
42   }
43 
44   // NOTE(liujisi): The factory setter is temporarily marked as package private.
45   // The way to provide customized implementations of maps for different
46   // platforms are still under discussion.  Mark it as private to avoid exposing
47   // the API in proto3 alpha release.
setMapFactory(MapFactory newMapFactory)48   /* public */ static void setMapFactory(MapFactory newMapFactory) {
49     mapFactory = newMapFactory;
50   }
51 
getMapFactory()52   public static MapFactory getMapFactory() {
53     return mapFactory;
54   }
55 
56   private static class DefaultMapFactory implements MapFactory {
forMap(Map<K, V> oldMap)57     public <K, V> Map<K, V> forMap(Map<K, V> oldMap) {
58       if (oldMap == null) {
59         return new HashMap<K, V>();
60       }
61       return oldMap;
62     }
63   }
64   private static volatile MapFactory mapFactory = new DefaultMapFactory();
65 
MapFactories()66   private MapFactories() {}
67 }
68