code: public Double getCharactersCharacterIdWallet(Integer characterId, String datasource, String ifNoneMatch,
              String token) throws ApiException {
          ApiResponse<Double> resp = getCharactersCharacterIdWalletWithHttpInfo(characterId, datasource, ifNoneMatch,
                  token);
          return resp.getData();
      }
docs: Get a character&#39;s wallet balance 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)
  @return Double
  @throws ApiException
  If fail to call the API, e.g. server error or cannot
  deserialize the response body