Question

我有两个班级：

子类：接待员类有两个方法ReadDoctorList（String readLine）和DisplayDoctorList（）。
父类：带有readLine方法的基础类，我将方法作为参数传递，该方法来自班级接待员。

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。我可以随时打印出值。 但是，如果我从TestClass中调用它，那么arraylist就会变空。

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

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());
    }

}

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，则应该有效

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

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

将上述代码更改为

readLines(this, pathusers, method);

使用反射调用方法后，为什么ArrayList中的值消失了？

1 个答案: