how to assign default value programmatically using reflection

import java.io.File;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Jackson2Example {

public static void main(String[] args) {
    Jackson2Example obj = new Jackson2Example();
    obj.run();
}

private void run() {
    ObjectMapper mapper = new ObjectMapper();

    Staff staff = createDummyObject();

    try {
        // Convert object to JSON string and save into a file directly
        mapper.writeValue(new File("D:\\staff.json"), staff);

        // Convert object to JSON string
        String jsonInString = 
mapper.writeValueAsString(staff);

System.out.println(jsonInString);

        // Convert object to JSON string and pretty print
        jsonInString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(staff);
        System.out.println(jsonInString);

    } catch (JsonGenerationException e) {
        e.printStackTrace();
    } catch (JsonMappingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private Staff createDummyObject() {

    Staff staff = new Staff();

    staff.setName("mkyong");
    staff.setAge(33);
    staff.setPosition("Developer");
    staff.setSalary(new BigDecimal("7500"));

    List<String> skills = new ArrayList<>();
    skills.add("java");
    skills.add("python");

    staff.setSkills(skills);

    return staff;

}

}

I would like to avoid createDummyObject method call and wants identity the attributes/types of class using java reflection. and want to below? 1.create a dynamic class instance 2. want to identify the class attributes example I the type was int then want to set set value like 999. same way for string ot list or map objects. how can a do that.