code: public com.squareup.okhttp.Call getCharactersCharacterIdWalletAsync(Integer characterId, String datasource,
              String ifNoneMatch, String token, final ApiCallback<Double> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = getCharactersCharacterIdWalletValidateBeforeCall(characterId, datasource,
                  ifNoneMatch, token, callback);
          Type localVarReturnType = new TypeToken<Double>() {
          }.getType();
          apiClient.executeAsync(call, localVarReturnType, callback);
          return call;
      }
docs: Get a character&#39;s wallet balance (asynchronously) Returns a
  character&#39;s wallet balance --- This route is cached for up to 120
  seconds SSO Scope: esi-wallet.read_character_wallet.v1
  
  @param characterId
  An EVE character ID (required)
  @param datasource
  The server name you would like data from (optional, default to
  tranquility)
  @param ifNoneMatch
  ETag from a previous request. A 304 will be returned if this
  matches the current ETag (optional)
  @param token
  Access token to use if unable to set a header (optional)
  @param callback
  The callback to be executed when the API call finishes
  @return The request call
  @throws ApiException
  If fail to process the API call, e.g. serializing the request
  body object