从文本文件中检索字符串数据并将其存储到对象中

Question

在我的代码示例中，您将看到很多代码。

但是，问题在于 restoreCourse 方法（在代码末尾），我试图将所有数据（已从 StorageManager 检索到）恢复到我的字符串数组（名为 lineBuffer）中，然后使用该数据用于恢复类 Course 的对象并在方法结束时返回它。

public class Course {

private String name;
private int courseID;
private String signUpCode;
private String courseGuide;
private String courseScheme;
private String courseGrade;
private String courseSpeed;
private String courseCredit;

public Course(String name,int courseID,String signUpCode,
        String courseGuide,String courseScheme,String courseSpeed,String 
courseCredit){
    this.name = name;
    this.courseID = courseID;
    this.signUpCode= signUpCode;
    this.courseGuide = courseGuide;
    this.courseScheme = courseScheme;
    this.courseSpeed = courseSpeed;
    this.courseCredit = courseCredit;
    this.courseGrade = "";
}
public int getCourseID(){
    return courseID;
}
public String getCourseName(){
    return name;
}
public String getSignUpCode(){
    return signUpCode;
}
public String getCourseScheme(){
    return courseScheme;
}
public String getCourseGuide(){
    return courseGuide;
}
public String getCourseGrade(){
    return courseGrade;
}
public String getCourseSpeed(){
    return courseSpeed;
}
public String getCourseCredit(){
    return courseCredit;
}

@Override
public String toString() {

    StringBuffer msg = new StringBuffer();
    msg.append (courseID);
    msg.append ("-");
    msg.append (name);
    msg.append ("-");
    msg.append (signUpCode);
    msg.append ("-");
    msg.append (courseGuide);
    msg.append ("-");
    msg.append (courseScheme);
    msg.append ("-");
    msg.append (courseGrade);
    msg.append ("-");
    msg.append (courseSpeed);
    msg.append ("-");
    msg.append (courseCredit);
    msg.append ("\n");
    return msg.toString();
}
}


public class FileCourseDAO implements CourseDAO {

public void  saveCourse(Course course){     

    StringBuffer dataBuffer = new StringBuffer();
    dataBuffer.append (course.getCourseID());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseName());
    dataBuffer.append ("-");
    dataBuffer.append (course.getSignUpCode());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseGuide());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseScheme());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseGrade());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseSpeed());
    dataBuffer.append ("-");
    dataBuffer.append (course.getCourseCredit());
    dataBuffer.append ("\n");

    StorageManager packer = StorageManager.getInstance();

    try {
        packer.storeStringData (dataBuffer.toString().trim());
    } catch (IOException e){
        System.out.println ("Storage manager Error:");
        e.printStackTrace ();
    }
}


public Course  restoreCourse(int courseID){
    StorageManager packer = StorageManager.getInstance();

    if (!packer.storeExists ()){
        System.out.println ("No file with data.");
        return;
    }
    try {
        String[] lineBuffer = null;
        List<String> dataBuffer = packer.readData();

        for (String dataLine : dataBuffer){
            lineBuffer = dataLine.split(" ");   
        }



    Course course = new Course ();

    } catch (IOException e) {
        System.out.println ("Error while reading data file.");
    }
    return course;
}
}

Answer 1

我想恢复对象（我保存在方法“saveCourse”中作为文本文件）并使用方法“restoreCourse”返回对象。

• 在saveCourse方法中，你序列化了-分隔的课程字段；因此，在拆分该字符串时，您必须使用 dataLine.split("-") 而不是 dataLine.split(" ")。
• 您正在创建Course 类的实例并在未初始化的情况下返回它。拆分后，使用这些数据初始化您的课程对象并将其返回给调用者。

以下代码可能有效：

public Course  restoreCourse(int courseID){
    StorageManager packer = StorageManager.getInstance();

    if (!packer.storeExists ()){
        System.out.println ("No file with data.");
        return;
    }
    Course course = null;
    try {
        String[] lineBuffer = null;
        List<String> dataBuffer = packer.readData();

        for (String dataLine : dataBuffer){
            lineBuffer = dataLine.split("-");
            if (lineBuffer.length > 7 && courseID == lineBuffer[0]) {
                course = new Course(lineBuffer[1],lineBuffer[0],lineBuffer[2], lineBuffer[3],lineBuffer[4],lineBuffer[6],lineBuffer[7] ); 
            }
        }
    } catch (IOException e) {
        System.out.println ("Error while reading data file.");
    }
    return course;
}

注意： 注意saveCourse()方法中构造函数参数的顺序和字段的顺序（它们的顺序不同）；我试图匹配它们，但请检查它们的顺序是否正确