Java code for modifying txt file contents will not function properly

Question

I am pretty new to java and working on an elementary project, experimenting with txt files. In this case, i have a txt file named "Activities" that contains a set of activities, each of which associated with an ID. The user then can decide wether to view, add or modify activities through the following code:

import java.io.*;
import java.util.*;


public class ActivitiesModification {
    private static Scanner x;
    public static void main(String[] args) throws IOException {
    
        String acfilepath = "C:\\Users\\John\\Desktop\\Activities.txt";
        
        File actxt = new File(acfilepath); //Name of the File Storing the activities (currently on desktop)
        
        FileWriter fw = new FileWriter(actxt, true);                      //FileWriter object representing the Activities txt file
        
        PrintWriter pw = new PrintWriter(fw);                             //PrintWriter object representing the Activities txt file
        
        Scanner sc = new Scanner(actxt);                                  //Scanner object which will scan through the txt file
        
        Scanner scinput = new Scanner(System.in);                         //Scanner object which scans user input
        
        System.out.println("What would you like to do? (view/add/modify)");
        
        String action = scinput.nextLine();                               //User input responsible for switch statement (Pre-UI temporary)
        
        switch(action) {
            case("view"):{
                System.out.println("The currently available activities are as follows:");
                viewActivities(actxt);
                break;
        }
            case("add"):{
                System.out.println("Please add the desired activity name");
                String addac = scinput.nextLine();
                int counter = 1;
                while(sc.hasNextLine()){
                    sc.nextLine();
                    counter++;
                }
                
                pw.println(counter + " " + addac);
                break;
        }
            case("modify"):{
            System.out.println("Please enter the ID of the activity whose name you would like to modify");
            
            String editTerm = scinput.nextLine();
            
            System.out.println("Please enter the new activity name");
            
            String newActivity = scinput.nextLine();
            
            editActivities(acfilepath, editTerm, newActivity);
            
            System.out.println("The activity name has been changed as requested. Would you like to view the full list of available activities?");
            
            String ds = scinput.nextLine();
            
            if(ds.equalsIgnoreCase("yes")) {
                
                viewActivities(actxt);
            }
        
        }
    }
    pw.close(); 
    scinput.close();
    sc.close(); 
    }


    
    public static void editActivities(String filepath, String editTerm, String newActivity) {
        String tempFile = "C:\\Users\\John\\Desktop\\temp.txt";
        File oldFile = new File(filepath);
        File newFile = new File(tempFile);
        String ID = ""; String activity = "";
        try {
            FileWriter fw1 = new FileWriter(tempFile, true);
            BufferedWriter bw1 = new BufferedWriter(fw1);
            PrintWriter pw1 = new PrintWriter(bw1);
            x = new Scanner(new File(filepath));
            
            while(x.hasNext()) {
                ID = x.next();
                activity = x.next();
                if(ID.equals(editTerm)) {
                    pw1.println(ID + " " + newActivity);
                }
                    else {
                        pw1.println(ID + " " + activity);
                    }

            }
            x.close();
            pw1.flush();
            pw1.close();
            bw1.close();
            fw1.close();
            oldFile.delete();
            File dump = new File(filepath);
            newFile.renameTo(dump);
        }
        catch(Exception e) {
            
        }
    }
    
    public static void viewActivities(File filepath) throws FileNotFoundException { // "filepath" will be the name of the file object which the scanner will scan through (actxt)
        Scanner sc = new Scanner(filepath);
        while(sc.hasNextLine()) {
            System.out.println(sc.nextLine());
        }
        sc.close();
    }
    
    
    }

However, for some reason the "modify" part of the code will not function properly. Intead of creating a new temp file, deleting the old one and renaming the tempfile activities. It just creates a temp file, transfers the appropriate contents and does not delete/rename.

I initially ran said code on another project (using the same files), and it worked fine. When transfering the code into a method in this project however it stopped working and I cannot figure out why.

Answer 1

On Windows, you cannot delete (or rename) file that is currently open.

It I am reading your code correctly:

• your editActivities method is being used to "edit" the file "C:\Users\John\Desktop\Activities.txt",

• at the point you call editActivities, you already have a FileWriter open for that file/

That's probably why the delete and rename are not happening.

---

As Federico points out, catching and squashing exceptions is problematic. It discards evidence of errors.

Also:

• You should check the result of File.delete and File.renameTo calls. Or better still, rewrite the code to use Files and Path rather than File.

• You seem to have a file open for reading and writing at the same time:

  FileWriter fw = new FileWriter(actxt, true);
  PrintWriter pw = new PrintWriter(fw);   
  Scanner sc = new Scanner(actxt);    // <<< === WHAT???
  

• You don't need to flush a Writer before closing it. The close() will flush any unwritten data.

• You don't need to close both the FileWriter AND the BufferedWriter that wraps it AND the PrintWriter that wraps that. Just close the PrintWriter

• You seem to be creating File objects and not using them.

• You should pay a lot more attention to what your code is actually doing. It currently looks chaotic. You do something, and then a few lines later do the same thing again ... as if you forgot you did it before.

• I don't understand why you declared x as a static field. It should be a local variable, since it is only used in one method.

• You should pay a lot more attention to getting the indentation right.