CODEWITHSUNDEEP
java
RyuggaHideki
RyuggaHideki

Reputation: 21

Deleting Lines on text file

I Tried this code for deleting certain Lines for my text file. However, when I delete my old file and replace it with new. The file won't be deleted nor be renamed. Can anyone help me with this one ? PS: I tried every method I can find but won't work I need it for my enrollment system project. Thanks in Advance

public static void deleteStudents() throws IOException, FileNotFoundException
{
    Scanner console = new Scanner(System.in);
    String SY, date;
    System.out.println("ENTER THE SCHOOL YEAR: SY: ");
    SY = console.next();

    int i = 0;

    Scanner print = new Scanner(new FileReader("Students- SY " + SY + " " + ".txt"));
    //display text file
    while(print.hasNextLine())
    {
        String stud= print.nextLine();
        System.out.println(stud);
    }   

    File inputFile = new File("Students- SY " + SY + " " + ".txt");
    File tempFile = new File("Students- SY " + SY + " " + ".txt.bak");

    BufferedReader reader = new BufferedReader(new FileReader(inputFile));
    BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

    String remove;
    String currentLine;

    System.out.println("ENTER STUDENT's ID NUMBER TO BE DELETED:  ");
    remove = console.next();
    while((currentLine = reader.readLine()) != null)
    {
        String trimmedLine = currentLine.trim();
        if(!trimmedLine.startsWith(remove)) 
        {
            writer.write(String.format("%s%n",currentLine)); 

        }
    }  
    //close reader/writer
    writer.close();
    reader.close();
  //delete file
    if(inputFile.delete())
    {
        tempFile.renameTo(inputFile);
    }
    else
    {
        System.out.println("FAIL");
    }

Upvotes: 1

Views: 437

Answers (3)

RyuggaHideki
RyuggaHideki

Reputation: 21

Guys Thanks for all your help. I just solved the problem of my code through your ideas. Here is my final code: 

public static void deleteStudents() throws IOException, FileNotFoundException
{
    Scanner console = new Scanner(System.in);
    String SY, date;
    System.out.println("ENTER THE SCHOOL YEAR: SY: ");
    SY = console.next();
    //System.out.println("ENTER DATE TO BE DISPLAYED(MM-DD-YY): ");
    //date = console.next();

    File inputFile = new File("Students- SY " + SY + ".txt");
    File tempFile = new File("Students- SY " + SY + ".txt.bak");

    BufferedReader reader = new BufferedReader(new FileReader(inputFile));
    BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

    Scanner print = new Scanner(new FileReader("Students- SY " + SY + ".txt"));
    while(print.hasNextLine())
    {
        String stud = print.nextLine();
        System.out.println(stud);
    }
    print.close(); 

    String remove;
    String currentLine;

    System.out.println("ENTER STUDENT's ID NUMBER TO BE DELETED:  ");
    remove = console.next();

    while((currentLine = reader.readLine()) != null)
    {
        //trim newline when comparing with lineToRemove
        String trimmedLine = currentLine.trim();
        if(!trimmedLine.startsWith(remove)) 
        {
            // if current line not start with lineToRemove then write to file
            writer.write(String.format("%s%n",currentLine)); 

        }
    }  
    writer.close();
    reader.close();

    if(!inputFile.delete())
    {
       tempFile.renameTo(inputFile);
        return;
    }
    if(!tempFile.renameTo(inputFile)){
        System.out.println("Could not rename file");
    }

Upvotes: 0

Jiri Tousek
Jiri Tousek

Reputation: 12450

You're not handling streams correctly. By the time you try to delete / rename the file, it is still open by Java due to the FileReader / Scanner held in print variable being still open. This will prevent the file from being deleted on Windows.

You need to wrap the reading from file in a try block and call print.close() in finally, or use try-with-resources.

Also, don't forget to close the reader and writer the same way (in finally or using try-with-resources).

Upvotes: 2

Si mo
Si mo

Reputation: 989

Use a method of the java.nio. package .. https://docs.oracle.com/javase/tutorial/essential/io/delete.html

It will show you much more information why the file isn't deleted or renamed.

Upvotes: 0

Related Questions