Comparable vs Comparator

public class Employee implements Comparable<Employee> {

    private Long id;

    private String name;

    private Double salary;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

    public Employee() {
    }

    public Employee(Long id, String name, Double salary) {
        this.id = id;
        this.name = name;
        this.salary = salary;
    }

    @Override
    public int compareTo(Employee o) {
        return (int) (this.id - o.id);
    }

    @Override
    public String toString() {
        return new ToStringBuilder(this)
                .append("id", id)
                .append("name", name)
                .append("salary", salary)
                .toString();
    }
}

public static void main(String[] args) {

        List<Employee> employeeList = new ArrayList<>();
        employeeList.add(new Employee(13L, "hello", 8000D));
        employeeList.add(new Employee(17L, "world", 10000D));
        employeeList.add(new Employee(13L, "test", 12000d));
        employeeList.add(new Employee(14L, "demo", 15000D));

        Collections.sort(employeeList);

        for (Employee e : employeeList) {

            System.out.println(e);
        }

        Collections.sort(employeeList, new Comparator<Employee>() {
            @Override
            public int compare(Employee o1, Employee o2) {
                int flag = (int) (o1.getId() - o2.getId());
                if (flag == 0) {
                    flag = (int) (o2.getSalary() - o1.getSalary());
                }

                return flag;
            }
        });

        System.out.println("comparator sort:");

        for (Employee e : employeeList) {

            System.out.println(e);
        }


    }

Employee@4d76f3f8[id=13,name=hello,salary=8000.0]
Employee@2d8e6db6[id=13,name=test,salary=12000.0]
Employee@23ab930d[id=14,name=demo,salary=15000.0]
Employee@4534b60d[id=17,name=world,salary=10000.0]
comparator sort:
Employee@2d8e6db6[id=13,name=test,salary=12000.0]
Employee@4d76f3f8[id=13,name=hello,salary=8000.0]
Employee@23ab930d[id=14,name=demo,salary=15000.0]
Employee@4534b60d[id=17,name=world,salary=10000.0]