Overwriting txt file in java

Question

The code I've written is supposed to overwrite over the contents of the selected text file, but it's appending it. What am I doing wrong exactly?

File fnew=new File("../playlist/"+existingPlaylist.getText()+".txt");
String source = textArea.getText();
System.out.println(source);
FileWriter f2;

try {
    f2 = new FileWriter(fnew,false);
    f2.write(source);
    /*for (int i=0; i<source.length();i++)
    {
        if(source.charAt(i)=='\n')
            f2.append(System.getProperty("line.separator"));
        f2.append(source.charAt(i));
    }*/
    f2.close();
} catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
}

EDIT

I tried making a new temp.txt file and writing the new contents into that, deleting this text file and renaming temp.txt to this one. Thing is, the deletion is always unsuccessful. I don't think I have to change user permissions for this do I?

Also, a part of my program lists all the files in this directory, so I'm guessing they're being used by the program and so can't be deleted. But why not overwritten?

SOLVED

My biggest "D'oh" moment! I've been compiling it on Eclipse rather than cmd which was where I was executing it. So my newly compiled classes went to the bin folder and the compiled class file via command prompt remained the same in my src folder. I recompiled with my new code and it works like a charm.

File fold=new File("../playlist/"+existingPlaylist.getText()+".txt");
fold.delete();
File fnew=new File("../playlist/"+existingPlaylist.getText()+".txt");
String source = textArea.getText();
System.out.println(source);

try {
    FileWriter f2 = new FileWriter(fnew, false);
    f2.write(source);
    f2.close();
} catch (IOException e) {
    e.printStackTrace();
}

Its working in my case too. May be something weird happening in your program. Try to work around the problem. Delete the whole content first and then start writing new content to same file. — Smit, Dec 05 '12 at 18:28
Tried that. Set it to a boolean variable. It's always false :\ — Karthik Balakrishnan, Dec 05 '12 at 18:38
I dont know whats going on in there. but try this. f2.write("".getBytes()); — Smit, Dec 05 '12 at 19:22

score 30 · Answer 1 · answered Dec 05 '12 at 18:22

30

Your code works fine for me. It replaced the text in the file as expected and didn't append.

If you wanted to append, you set the second parameter in

new FileWriter(fnew,false);

to true;

answered Dec 05 '12 at 18:22

user1757442

326
2
5

score 10 · Accepted Answer · edited Feb 20 '20 at 10:35

SOLVED

My biggest "D'oh" moment! I've been compiling it on Eclipse rather than cmd which was where I was executing it. So my newly compiled classes went to the bin folder and the compiled class file via command prompt remained the same in my src folder. I recompiled with my new code and it works like a charm.

File fold = new File("../playlist/" + existingPlaylist.getText() + ".txt");
fold.delete();

File fnew = new File("../playlist/" + existingPlaylist.getText() + ".txt");

String source = textArea.getText();
System.out.println(source);

try {
    FileWriter f2 = new FileWriter(fnew, false);
    f2.write(source);
    f2.close();

} catch (IOException e) {
    e.printStackTrace();
}

score 5 · Answer 3 · edited Feb 20 '20 at 10:36

5

Add one more line after initializing file object

File fnew = new File("../playlist/" + existingPlaylist.getText() + ".txt");
fnew.createNewFile();

edited Feb 20 '20 at 10:36

RubioRic

2,442
4
28
35

answered Dec 05 '12 at 18:14

Android Killer

18,174
13
67
90

1

`new File` is sufficient to *Create a new file* – Dec 05 '12 at 18:16
I'm just setting path to an existing file. – Karthik Balakrishnan Dec 05 '12 at 18:19
9

@ALJIMohamed no, `new File` just creates the Java object representing an abstract concept of a file. Otherwise, there would be no point in having an `exists()` method as the file would always exist after `new File`. – Jim Garrison Dec 05 '12 at 18:19
1

@Torcellite yes ofcourse you are setting path, but as you want to overrtite, it's same to create new file. – Android Killer Dec 05 '12 at 18:22
@AndroidKiller. Using `false` as 2nd parameter to `FileWriter` sets the append mode to false. The original code in OP should work. Don't know why it isn't working. It's working in my case. – Rohit Jain Dec 05 '12 at 18:23
@RohitJain It works on Linux and Windows for me as expected, too. – nullpotent Dec 05 '12 at 18:24

score 1 · Answer 4 · answered Dec 05 '12 at 18:19

1

This simplifies it a bit and it behaves as you want it.

FileWriter f = new FileWriter("../playlist/"+existingPlaylist.getText()+".txt");

try {
 f.write(source);
 ...
} catch(...) {
} finally {
 //close it here
}

answered Dec 05 '12 at 18:19

nullpotent

9,162
1
31
42

1

It's the same thing. It's still appending text – Karthik Balakrishnan Dec 05 '12 at 18:22

user7471800 · Answer 5 · 2017-01-26T01:31:42.093

The easiest way to overwrite a text file is to use a public static field.

this will overwrite the file every time because your only using false the first time through.`

public static boolean appendFile;

Use it to allow only one time through the write sequence for the append field of the write code to be false.

// use your field before processing the write code

appendFile = False;

File fnew=new File("../playlist/"+existingPlaylist.getText()+".txt");
String source = textArea.getText();
System.out.println(source);
FileWriter f2;

try {
     //change this line to read this

    // f2 = new FileWriter(fnew,false);

    // to read this
    f2 = new FileWriter(fnew,appendFile); // important part
    f2.write(source);

    // change field back to true so the rest of the new data will
    // append to the new file.

    appendFile = true;

    f2.close();
 } catch (IOException e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
 }

score 1 · Answer 6 · answered Mar 07 '23 at 18:47

A much cleaner way since Java 11, assuming you're sure that the file already exists:

Files.writeString(Paths.get("path/to/file"), "str to write", StandardOpenOption.TRUNCATE_EXISTING);

The above will throw if the file doesn't exist. In that case:

Path newFile = Paths.get("path/to/file.txt");
if(!Files.exists(newFile)) {
    Files.writeString(newFile, "some str", StandardOpenOption.CREATE);
} else {
    Files.writeString(newFile, "some str", StandardOpenOption.TRUNCATE_EXISTING);
}

Check the StandardOpenOption for options:

CREATE - Create a new file if it does not exist
TRUNCATE_EXISTING - If the file already exists and it is opened for WRITE access, then its length is truncated to 0
APPEND - write to the end of the file rather than the beginning

etc.

Overwriting txt file in java

6 Answers6

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