提取对象列表，然后根据方法进行检查，然后返回新列表

Question

sM是该类的一个实例，运行方法staffCanWork时，它应返回一个可以在给定日期和时间工作的人员对象的列表，但是，在运行该方法时，它会导致指针错误为空。

在静态void main中测试方法；

 Date date = Date.valueOf(LocalDate.now());
        List<Staff> staff = sM.staffCanWork(date, Time.valueOf(LocalTime.now()));
        for(int i = 0; i < staff.size(); i++){
            System.out.println(staff.get(i).getId());
        }

使用hibernate的getStaff（）方法使用hibernate填充带有人员对象的列表。

    public List<Staff> getStaff(){
        List staff =null;
        Session session = factory.openSession();
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            TypedQuery query = session.getNamedQuery("getStaff");;
            staff = query.getResultList();
        }catch (HibernateException e){
            e.printStackTrace();
        }return staff;
    }

staffCanWork方法，检查列表以查看员工是否可以按给定的日期和时间进行工作。

    public List<Staff> staffCanWork(Date date, Time time){
        List<Staff> staff = getStaff();
        List<Staff> staff1 = null;
        for(int i = 0; i < staff.size(); i++){
            if(staff.get(i).getDoctor() == null){
                if(staff.get(i).getNurse().canWork(date, time)) staff1.add(staff.get(i));
            }
            else {
                if(staff.get(i).getDoctor().canWork(date, time)) staff1.add(staff.get(i));
            }
        }
        System.out.println(staff1.get(0).getId() + "test");
        return staff1;
    }

方法可以工作

public boolean canWork(Date date, Time time){
        Boolean canWork =false;
        Boolean aM = false;

        if(time.getTime() < 12){ aM = true;}
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("E");
        simpleDateFormat.format(date);
        if(aM = true) {
            switch (simpleDateFormat.format(date)) {
                case "Mon": if (getMondayAM() == true) canWork = true;
                    break;
                case "Tue" :if (getTuesdayAM() == true) canWork = true;
                    break;
                case "Wed" :if (getWednesdayAM() == true) canWork = true;
                    break;
                case "Thu" :if (getThursdayAM() == true) canWork = true;
                    break;
                case "Fri" :if (getFridayAM() == true) canWork = true;
                    break;
                case "Sat" :if (getSaturdayAM() == true) canWork = true;
                    break;
                case "Sun" :if (getSundayAM() == true) canWork = true;
                default: return false;
            }
        }
        switch (simpleDateFormat.format(date)) {
            case "Mon": if (getMondayPM() == true) canWork = true;
                break;
            case "Tue" :if (getTuesdayPM() == true) canWork = true;
                break;
            case "Wed" :if (getWednesdayPM() == true) canWork = true;
                break;
            case "Thu" :if (getThursdayPM() == true) canWork = true;
                break;
            case "Fri" :if (getFridayPM() == true) canWork = true;
                break;
            case "Sat" :if (getSaturdayPM() == true) canWork = true;
                break;
            case "Sun" :if (getSundayPM() == true) canWork = true;
            default: return false;
        }
        return canWork;
    }