How to convert a Java object to JSON

import com.google.gson.Gson;
public class main
{
    public class Employee {
        private String name;
        private int age;
    }
    public static String convertUsingGson(Employee e)
    {
        Gson gson = new Gson();
        String employeeJson = gson.toJson(e);
        return employeeJson;
    }
}

import java.io.File;
import com.fasterxml.jackson.databind.ObjectMapper;
public class main{
   public static void main(String[] args) {
      ObjectMapper mapper = new ObjectMapper();
      Employee emp = createEmployee();
      try {
         // Java objects to JSON string
         String jsonString = mapper.writeValueAsString(emp);
         System.out.println(jsonString);
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
   private static Employee createEmployee() {
      Employee e = new Employee();
      e.setName("Jon");
      e.setAge(25);
      return e;
   }
}