Refactoring.java

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import com.google.gson.Gson;

import java.util.Arrays;


public class Refactoring {

    final static Converter<Object, String> JSON_CONVERTER = (object) -> {
        Gson gson = new Gson();
        return gson.toJson(object);
    };

    final static Converter<Object, String> XML_CONVERTER = (object) -> {
        XmlMapper xmlMapper = new XmlMapper();
        try {
            return xmlMapper.writeValueAsString(object);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    };


    public static void main(String[] args) throws Exception {

        Employee regularEmployee = new Employee(39983, 20000, JSON_CONVERTER);
        Contractor contractor = new Contractor(1111, 60000, 5000, XML_CONVERTER);

        Arrays.asList(regularEmployee, contractor).forEach(
                employee -> {
                    employee.makePayment();
                    employee.printReport();
                }
        );

    }


    @FunctionalInterface
    interface Converter<T, R> {
        R serialize(T var1);
    }

    static class Employee {

        Converter<Object,String> converter;
        int accountNumber;
        int salary;

        public int getAccountNumber() {
            return accountNumber;
        }

        public int getSalary() {
            return salary;
        }

        public Employee(int accountNumber, int salary, Converter<Object,String> converter) {
            this.accountNumber = accountNumber;
            this.salary = salary;
            this.converter = converter;
        }

        public void printReport() {
            System.out.println("printing regular employee details in json format: "
                    + converter.serialize(this));
        }

        public void makePayment() {
            System.out.println("Processing payment for " + accountNumber + " amount: " + (salary));
        }
    }

    static class Contractor extends Employee {
        int commission;

        public int getCommission() {
            return commission;
        }

        public Contractor(int accountNumber, int salary, int commission, Converter<Object,String> converter) {
            super(accountNumber, salary, converter);
            this.commission = commission;
        }

        @Override
        public void makePayment() {
            System.out.println("Processing payment for " + accountNumber
                    + " amount: " + (salary - commission));
        }
    }


}