private static LinkedHashMap<KnownVersion, ConcurrentMap<MessageType, Command>> initializeAllCommands() {
    final LinkedHashMap<KnownVersion, ConcurrentMap<MessageType, Command>> allCommands =
        new LinkedHashMap<>();

    final ConcurrentMap<MessageType, Command> gfe81Commands = buildGfe81Commands();
    allCommands.put(KnownVersion.GFE_81, gfe81Commands);

    final ConcurrentMap<MessageType, Command> gfe90Commands =
        buildGfe90Commands(allCommands.get(KnownVersion.GFE_81));
    allCommands.put(KnownVersion.GFE_90, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_1_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_1_1, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_2_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_3_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_4_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_5_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_6_0, gfe90Commands);
    allCommands.put(KnownVersion.GEODE_1_7_0, gfe90Commands);

    final ConcurrentMap<MessageType, Command> geode18Commands =
        buildGeode18Commands(allCommands.get(KnownVersion.GEODE_1_7_0));
    allCommands.put(KnownVersion.GEODE_1_8_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_9_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_10_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_11_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_12_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_12_1, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_13_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_13_2, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_14_0, geode18Commands);
    allCommands.put(KnownVersion.GEODE_1_15_0, geode18Commands);

    // as of GEODE_1_15_0 we only create new command sets when the
    // client/server protocol changes

    return allCommands;
  }
Iterate through all the Geode versions add a command to the map for that version

@return returns true if command was registered or same command was already registered,
        otherwise false.
@throws InternalGemFireError if a different command was already registered.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/CommandInitializer.java