Question

我是Java的初学者，我需要帮助。我只想从文本文件中获取值，然后将这些值与Object的变量进行比较。但不知何故，它以错误的方式运作。我花了超过4-5个小时而陷入困境。这是我的代码。

    private List<Course> hs = new ArrayList<>();
    private List<String> list = new ArrayList<>();
    private String[] properties;

public void readLines() {
    try (BufferedReader br = Files.newBufferedReader(Paths.get(Instructor.root.toString()), StandardCharsets.UTF_8)) {
        list = br.lines().collect(Collectors.toList());

        for(int i = 0; i < list.size(); i++) {
            properties = list.get(i).split("%");
            Course course = new Course(properties[0]);
            Undergraduate undergraduate = new Undergraduate(properties[0],properties[1], properties[2], properties[3]);
            if(hs.size() != 0 && isObjectInSet(course, hs)) {
                getIfObjectInSet(course, hs).setUndergraduates(undergraduate);
            }else {
                course.setUndergraduates(undergraduate);
                hs.add(course);
            }}
    }catch (IOException e) {
        System.err.println(e);
    }
    //System.out.println(hs.size());
}

    public boolean isObjectInSet(Course object, List<Course> hs) {
    boolean result = false;


    for (int i = 0; i < hs.size(); i++) {
        String arrayedCourse =  hs.get(i).getCourseID();
        String objectsID = object.getCourseID();
        if (objectsID.equals(arrayedCourse)) {
            result = true;
            break;
        }
    }return result; }

public Course getIfObjectInSet(Course object, List<Course> set) {
    Course result = null;

    for (int i = 0; i < set.size(); i++) {
        if (isObjectInSet(object, set)) {
            result = set.get(i);
            break;
        } }return result;
}}

这是课程类'变量：

public class Course {
private String courseID;
private ArrayList<Undergraduate> undergraduates = new ArrayList<>();

课程班级中的setUndergraduates

    public void setUndergraduates(Undergraduate undergraduates) {
    ArrayList<Undergraduate> students = this.undergraduates;
    students.add(undergraduates);
    this.undergraduates = students;
}

这是文本文件结构

BIM101％11111111111％帕帕％25

这是调试。两个字符串相等但它告诉它们不是

https://i.stack.imgur.com/BOO5d.jpg

Answer 1

请在您的班级Course中覆盖方法declare，方法是添加要比较的字段。 Hint

Answer 2

我认为问题出在您的getIfObjectInSet()中 - 它使用isObjectInSet()，但如果任何元素匹配，则返回true，而不是仅仅当前元素匹配。

无论如何，你最好在这里使用Map - 你可以完全避免这两个功能：

private Map<String, Course> courses = new TreeMap<>();

public void readLines(Path file) {
    try (BufferedReader br = Files.newBufferedReader(file, StandardCharsets.UTF_8)) {
        br.lines().forEach(line -> {
            String[] parts = line.split("%");
            String courseId = parts[0];

            Undergraduate undergraduate = new Undergraduate(courseId, parts[1], parts[2], parts[3]);

            Course course = courses.get(courseId);
            if (course == null) {
                course = new Course(courseId);
                courses.put(courseId, course); 
            }

            course.setUndergraduates(undergraduate); // rename to addUndergraduate?
        });
    } catch (IOException e) {
        throw new RuntimeException(e); // don't just continue on errors..
    }
}

String.equals（）不起作用，哪些字符串来自文本文件

2 个答案: