Group13CleanSweep_SE_459 In Intellij, we need to add the gson jar and put it into the project Download Gson .jar file from http://www.java2s.com/Code/Jar/g/Downloadgson222jar.htm Go to File > Project Structure > Modules > Dependencies Click the plus sign > JARs or Directories > navigate to where you saved gson-2.2.2.jar