java - 为什么使用反射调用方法后ArrayList中的值消失了？

Question

我有两门课:

1. 子类:接待员类，具有两个方法 ReadDoctorList(String readLine) 和 DisplayDoctorList()。

2. 父类:带有 readLine 方法的基类，我在其中传递一个方法作为参数，该方法来自类接待员。

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我的想法是逐行读取txt文件并提取一些行并将它们存储在ArrayList中。我可以即时打印出这些值。 但是，如果我从 TestClass 调用它，数组列表就会变成空。

我们将非常感谢您的回答!

Output: 
Tonny Bob
Mike tyson
The size is: 0


txt file:
    Tonny,Bob,abc,abc,D
    Mike,tyson,abc,abc,D
    Laura,jack,abc,abc,P
    Jimmy,viva,abc,abc,P

<小时/>

public class TestClass {
    public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
        Receptionist obj = new Receptionist();
        obj.DisplayDoctorList();
        System.out.println("The size is: " + obj.doctorlist.size());
    }

}

<小时/>

public class Base {
    String pathusers = "/Users/MacTonish/users.txt";
    ArrayList<String> doctorlist = new ArrayList<String>();

    public void readLines(Object instance, String path, Method method)
            throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        try {
            File txt = new File(path);
            BufferedReader reader = new BufferedReader(new FileReader(txt));
            String readLine = null;
            while ((readLine = reader.readLine()) != null) {
                method.invoke(instance, readLine); //something is fishy here.
            }
            reader.close();
        } catch (

        IOException e) {
            e.printStackTrace();
        }
    }
}

class Receptionist extends Base {

    public void DisplayDoctorList() throws NoSuchMethodException, SecurityException, IllegalAccessException,
            IllegalArgumentException, InvocationTargetException {
        Method method = Receptionist.class.getMethod("ReadDoctorList", String.class);
        readLines(new Receptionist(), pathusers, method);
    }

    public void ReadDoctorList(String readLine) {
        String[] token = readLine.split(",");
        if (token[4].equals("D")) {
            doctorlist.add(token[0] + " " + token[1]);   
            System.out.println(token[0] + " " + token[1]); //Print out is ok.
        }

    }
}

Answer 1

如果您对接待员代码进行以下更改，它应该可以工作

    //readLines(new Receptionist(), pathusers, method);

    //Here you are creating a new object but while printing you are using last created Object of ReceptionList

将上面一行代码改为

readLines(this, pathusers, method);