code: public JWT getJWT() {
          AccountData accountData = getAccountData(); // Update access token if
                                                      // needed
          if (accountData == null) {
              return null;
          }
          try {
              String accessToken = accountData.getAccessToken();
              if (accessToken == null) {
                  return null;
              }
              String[] parts = accessToken.split("\\.");
              if (parts.length != 3) {
                  return null;
              }
              Gson gson = new GsonBuilder().registerTypeAdapter(JWT.Payload.class, new JWT.PayloadDeserializer())
                      .create();
              JWT.Header header = gson.fromJson(new String(Base64.getUrlDecoder().decode(parts[0])), JWT.Header.class);
              JWT.Payload payload = gson.fromJson(new String(Base64.getUrlDecoder().decode(parts[1])), JWT.Payload.class);
              String signature = parts[2];
              return new JWT(header, payload, signature);
          } catch (JsonSyntaxException ex) {
              return null;
          }
      }
docs: Get JWT (JSON Web Token) WARNING: The JWT is unverified. Verifying the
  JWT is beyond the scope of this library. As ESI will verify the token
  when used. See the SSO documentation for JWT Token validation for
  details:
  https://github.com/esi/esi-docs/blob/master/docs/sso/validating_eve_jwt
  .md
  
  @return Unverified JWT or null