Constructor of class:

OfflineCache(boolean onlineMode);

Loading from the Config

OfflineCache offlineCache = ...
Config rawData = ...
for(String uuid : rawData.getKeys())
  try {
    offlineCache .setLookup(UUID.fromString(uuid), rawData.getString(uuid));
  }catch(Exception err) {}

Saving to the Config

OfflineCache offlineCache = ...
Config rawData = offlineCache .saveToConfig();

Lookup for player's query by player's name

OfflineCache offlineCache = ...
Query query = offlineCache.lookupQuery(playerName);

Lookup for player's query by player's uuid

OfflineCache offlineCache = ...
Query query = offlineCache.lookupQuery(playerUuid);

Lookup for player's uuid by player's name (Mojang - Require internet connection)

OfflineCache offlineCache = ...
UUID uuid = offlineCache.lookupIdFromMojang(playerName);

Lookup for player's corrent name by player's name (Mojang - Require internet connection)

OfflineCache offlineCache = ...
String nickname = offlineCache.lookupNameFromMojang(playerName);

Saving UUID & Player name to the OfflineCache (Probably PlayerLoginEvent)

OfflineCache offlineCache = ...
offlineCache.setLookup(playerUuid, playerName);

Examples

OfflineCache offlineCache = new OfflineCache(Bukkit.getOnlineMode());
Config rawData = new Config("plugins/TheAPI/Cache.dat");
for(String uuid : rawData.getKeys())
  try {
    offlineCache .setLookup(UUID.fromString(uuid), rawData.getString(uuid));
  }catch(Exception err) {}

Query query = offlineCache.lookupQuery("StraikerinaCZ");
if(query==null) {
  //StraikerinaCZ doesn't exist!
  return;
}
String name = query.getName();
UUID uuid = query.getUUID();