java重载equals和hashCode

class Employee {

    private int salary;
    private java.util.Date hireDay;
    private String name;

    public int getSalary() {
        return salary;
    }

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

    public Date getHireDay() {
        return hireDay;
    }

    public void setHireDay(Date hireDay) {
        this.hireDay = hireDay;
    }

    public String getName() {
        return name;
    }

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

    public Employee(String name, int salary, Date hireDay) {
        this.name = name;
        this.hireDay = hireDay;
        this.salary = salary;
    }

    public Employee() {

    }

    static private HashMap<String, String> dict = new HashMap<String, String>();

    static {
        num = 0;
/*        dict.put("1","Employee");
        dict.put("2","Employee");*/
    }

    @Override
    public String toString() {

        if (hireDay == null)
            hireDay = Calendar.getInstance().getTime();
        SimpleDateFormat formatter;
        formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return String.format("name:%s,salary:%d,hireDay:%s", name, salary, formatter.format(hireDay));
    }

    static int num;

    public static int getNum() {
        return num;
    }

    public static int setNum(int a) {
        num += a;
        return getNum();
    }

    @Override
    public int hashCode() {
        //0
        int result = 11;
        result = result * 17 + (name == null ? 0 : name.hashCode());
        result = result * 17 + (hireDay == null ? 0 : hireDay.hashCode());
        //result=result*17+salary;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null || !(obj instanceof Employee))
            return false;
        if (this == obj)
            return true;
        Employee instance = (Employee) obj;

        return name.equals(instance.name) && hireDay.equals(instance.hireDay);
    }
}