CODEWITHSUNDEEP
javaoverwritefilewriter
Karthik Balakrishnan
Karthik Balakrishnan

Reputation: 4383

Overwriting txt file in java

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();
}

Upvotes: 39

Views: 192382

Answers (6)

Andrejs
Andrejs

Reputation: 11901

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.

Upvotes: 3

Android Killer
Android Killer

Reputation: 18489

Add one more line after initializing file object

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

Upvotes: 5

Karthik Balakrishnan
Karthik Balakrishnan

Reputation: 4383

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();
}

Upvotes: 10

user7471800
user7471800

Reputation: 11

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();
 }

Upvotes: 1

user1757442
user1757442

Reputation: 326

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;

Upvotes: 30

nullpotent
nullpotent

Reputation: 9260

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
}

Upvotes: 1

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