为什么这只是复制txt文件中的最后一行？

Question

我正在处理此代码的特定部分，该部分允许用户更改有关保存在txt文件中的项目的详细信息。每个项目都保存在单独的行上，如下所示：

1, Project House Tyson, Building Type: House, Project Address: 365 Long Ave, ERF Number: 12jk, Total Fee Charged: 1000, Amount Paid to Date: 900, Project Deadline: 01 October 2021, Project Contractor: Bob, Lead Architect: Ted, Client: Mike Tyson, Complete: No

如果用户输入“c”，将要求他们在菜单中键入项目名称，然后输入“a”更改日期。这一切都很好，除了不只是更改txt文件中所需行的日期，而是用文件中最后一行的副本替换项目。

它最终看起来像这样(注意第3行的项目现在是第5行的副本，但是有了新的日期):

1, Project House Tyson, Building Type: House, Project Address: 365 Long Ave, ERF Number: 12jk, Total Fee Charged: 1000, Amount Paid to Date: 900, Project Deadline: 01 October 2021, Project Contractor: Bob, Lead Architect: Ted, Client: Mike Tyson, Complete: No
2, Project House Jordan, Building Type: house, Project Address: 75 Elgin Rd, ERF Number: mj23, Total Fee Charged: 1000, Amount Paid to Date: 900, 11 October 2021, Project Contractor: Bob, Lead Architect: Ted, Client: Mike Jordan, Complete: No
5, Project test3, Building Type: house, Project Address: 3i, ERF Number: 2k2k, Total Fee Charged: 10101, Amount Paid to Date: 2020, 05 October 2021, Project Contractor: ten, Lead Architect: dido, Client: kokolk, Complete: No
4, Project test2, Building Type: hh, Project Address: jhj, ERF Number: hjh, Total Fee Charged: hjh, Amount Paid to Date: hjh, Project Deadline: hjh, Project Contractor: hjh, Lead Architect: hjh, Client: hjh, Complete: No
5, Project test3, Building Type: house, Project Address: 3i, ERF Number: 2k2k, Total Fee Charged: 10101, Amount Paid to Date: 2020, Project Deadline: 01 December 2021, Project Contractor: ten, Lead Architect: dido, Client: kokolk, Complete: No

这是用户与菜单交互的主要方法。我觉得问题不在这里，只是供一些参考:

public class MenuV4 extends ExceptionHandling {

public static void main (String args[]) throws IOException, ParseException {
    
    //File object to store project info
    try {
        File file = new File("C:\\CurrentProjects.txt");
        
    }catch (Exception e){
        System.out.println("Error at main");
    }
    
    //Options at main menu displayed to user
    while (true) {
        System.out.println("\nPlease choose a number option from the menu below: "
                + "\na) View Projects"
                + "\nb) Add Project"
                + "\nc) Edit Project"
                + "\nd) Finalize a Project"
                + "\ne) View Incomplete Projects"
                + "\nf) View Overdue Projects"
                + "\ng) Exit program");
    
    //Checking user input is valid with string check method from Exception Handling class
    //fileCheck boolean makes sure that there is at least one project in the file object
    String userChoice = stringCheck("menu choice"); 
    boolean projects = fileCheck();
    
    if ((projects == true) && (userChoice.equals("a") || userChoice.equals("A"))) {  
        Projects object = new Projects();
        object.viewProjects();
        
    
    } else if (userChoice.equals("b") || userChoice.equals("B")) {  
        CreateProject setNew = new CreateProject();
        setNew.CreateProject();
        
    //Here is where the problem is, user enters 'c' to edit a project 
    } else if ((projects == true) && (userChoice.equals("c") || userChoice.equals("C"))) {  
        
        //User is prompted to enter the number of the project they would like to edit
        //This input is put through stringCheck
        //User can choose to change due date or fees paid
        System.out.println("Please enter the name of the project you wish to update: \n");
        String projectInfo = stringCheck("project number");
        System.out.println("Would you like to:" + 
                "\na) Edit the project due date or" +
                "\nb} Edit the total amount paid of the fee to date?");
        
        //Again put through stingCheck
        String editChoice = stringCheck("edit choice");
        Projects obj1 = new Projects();
        int lineCount = obj1.loadProjects(projectInfo);
        obj1.updateProject(editChoice, lineCount);  

找到他们正在寻找的项目的方法如下所示:

public class Projects extends ExceptionHandling{

public int loadProjects(String projectInfo) {
    String[] info = new String[12];  
    int lineCount = 1;  
    
    // A new file object is created and a while loop used to run through lines in the test file.
    // Line info is then split and stored in the array.
    // While loop is exited if the second index in the array matches projectInfo parameter (typed in by user)
    try {
        File file = new File("C:\\CurrentProjects.txt");  
        Scanner projectFile = new Scanner(file);
        
        while (projectFile.hasNextLine()) {  
            
            info = projectFile.nextLine().split(", "); 
            
            if ((info[1].equalsIgnoreCase("Project " + projectInfo)) || (info[1].equalsIgnoreCase(projectInfo))) {
                break;  
                
            } else {
                lineCount++; 
                
            }
        }
    } catch (FileNotFoundException e) {  
        System.out.println("Error.");

    }
    return lineCount;  
}

更改项目截止日期的方法看起来像这样，也在Projects类中：我认为问题出在这个方法的某个地方。

public void updateProject (String editChoice, int lineCount) {
    
    ArrayList<String> infoArray = new ArrayList<String>();
    String[] info = new String[12];
    int findLine = 1;
    
    // A file object is created and a while loop used to run through each line of the text file.
    // Each line of project information is added to the ArrayList.
    try {
        File file = new File("C:\\CurrentProjects.txt");
        Scanner projectFile = new Scanner(file);
        
        while (projectFile.hasNextLine()) {
            infoArray.add(projectFile.nextLine());  
    
        }
    
    } catch (FileNotFoundException e) {  
        System.out.println("Error51");
    }
    
    //Create another file object.
    // Each line of the text file is run through and when the lineCount matches the findLine variable, then the line info is split.
    // That specific split line info is then stored in the info string array.
    try {
        File file = new File("C:\\CurrentProjects.txt");
        Scanner projectFile = new Scanner(file);
        
        while (projectFile.hasNextLine()) {
            if (findLine == lineCount) {
                info = projectFile.nextLine().split(", ");
                System.out.println(Arrays.toString(info));
                
            } else if (findLine != lineCount) {  // Line count incremented if match is not made.
                findLine++;
            }
        }
    
    } catch (FileNotFoundException e) {
        System.out.println("Error.");
    }
    
     //If the user chose edit choice 'a', they are prompted for a new due date.
     //The new due date info is then inserted into index number 7 in the info array
     //The info array is then converted into a string, with extra characters removed ("[]")
     //The finalised string 'newLine' is then inserted into the correct index of the infoArray ArrayList (i.e. lineCount -1).
     //The same process is followed for edit choice 'b', except they are prompted for a new total amount, which is replaced at index 6 in the info array.
    if (editChoice.equals("a") || editChoice.equals("A")) {
        System.out.println("Please enter a new project due date: ");
        String newDeadline = stringCheck("due date");
        info[7] = newDeadline;
        String newInfo = Arrays.toString(info);
        String changeLine = newInfo.replace("[", "");
        String newLine = changeLine.replace("]", "");
        infoArray.set(lineCount-1, newLine);
        
    } else if (editChoice.equals("b") || editChoice.equals("B")) {
        System.out.println("Please enter a new total amount of the fee paid to date:");
        String newAmount = stringCheck("new total amount");
        info[6] = newAmount;
        String newInfo = Arrays.toString(info);
        String changeLine = newInfo.replace("[", "");
        String newLine = changeLine.replace("]", "");
        infoArray.set(lineCount-1, newLine);
        
    }
    
    
    //Re-write to the CurrentProjects.txt file.
    try {
        Formatter F = new Formatter("C:\\CurrentProjects.txt");
        for (String element : infoArray) {
            F.format("%s", element + "\r\n");
        }
        System.out.println("Project successfully updated.");  
        F.close();
        
    } catch (Exception e) {
        System.out.println("Error.");  
        
    }   
}

Answer 1

我过去一直在编辑txt文件，我也遇到过这个问题。

我认为问题在于它正在访问以前版本的信息数组列表，在你的情况下，infoArray。

所以为了解决这个问题，我有一个方法可以从infoArray中删除所有数据，这样就无法从以前版本的txt文件中访问任何信息。这是一种方法：

public void removeInfo(ArrayList<String> info) {
    while(info.size() > 0) {
        info.remove(0);
    }
}

我不完全确定这个remove方法应该在你的代码中的什么位置，但是我希望它有所帮助。