核心技术出错了,该怎么解决

import java.util.*;public class EmployeeTest {    /**     * @param args     */    public static void main(String[] args) {        Employee[] staff = new Employee[3];                staff[0] = new Employee("K",75000,1987,12,15);        staff[1] = new Employee("L",50000,1989,10,1);        staff[2] = new Employee("P",40000,1990,3,15);                for(Employee e:staff)            e.raiseSalary(5);                for(Employee e:staff)            System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay=" + e.getHireDay());        // TODO Auto-generated method stub    }}class Employee{    public Employee(String n,double s, int year, int month,int day){        name = n;        salary = s;                GregorianCalendar calendar = new GregorianCalendar(year,month-1,day);            hireDay = Calendar.getTime();    }        public String getName(){        return name;    }        public double getSalary()    {        return salary;    }    public Date getHireDay(){        return hireDay;    }    public void raiseSalary(double byPercent){        double raise = salary * byPercent/100;        salary += raise;            }        private String name;    private double salary;    private Date hireDay;    }

hireDay = calendar.getTime();