Filewriter will not append text to newly created file

Question

I'm fairly new to Java. I was trying to add "List:" to the beginning of a new text file if it doesn't exist. Instead, the text file is blank, with the input below a line of blank space.

File hi = new File("hi.txt");
try{
  if(!hi.exists()){
    System.out.printf("\nCreating 'hi.txt'."); 
    hi.createNewFile();
    String hello = "List:";
    new FileWriter(hi).append(hello);
  }
  else{
    System.out.printf("\nWriting to 'hi.txt'");
  }
  FileWriter writeHere = new FileWriter(hi, true);
  String uling = "hi";
  writeHere.append(uling);
  writeHere.close();
}
//error catching
catch(IOException e){
  System.out.printf("\nError. Check the file 'hi.txt'.");}

Answer 1

The problem is with this line:

new FileWriter(hi).append(hello);

You're not closing the writer, which means:

• The file handle is potentially still open, which could cause problems when you try to write to it
• You're not flushing the writer, so the input may get lost

You should also get in the habit of using try-with-resources to acquire and then automatically close the writer, even if an exception occurs.

Personally, I'd change the structure of your code somewhat so you only open the file once:

File hi = new File("hi.txt");
boolean newFile = !hi.exists();
System.out.printf("%n%s 'hi.txt'.", newFile ? "Creating" : "Writing to");
try (Writer writer = new FileWriter(hi, true)) {
    // Note: if you've already got a string, you might as well use write...
    if (newFile) {
        writer.write("List:");
    }
    writer.write(uling);
}
catch(IOException e) {
  System.out.printf("\nError. Check the file 'hi.txt'.");
}

Answer 2

Pass true as a second argument to FileWriter to turn on "append" mode (in the first FileWriter you have created).

Also, you should create the variable FileWriter , and close it after appending "List:", as you leave the scope of that variable.

So, I would edit the code as following:

File hi = new File("hi.txt");
try {
    if (!hi.exists()) {
        System.out.printf("\nCreating 'hi.txt'.");
        hi.createNewFile();
        String hello = "List:";
        FileWriter writer = new FileWriter(hi, true);
        writer.append(hello);
        writer.close();
    } else {
        System.out.printf("\nWriting to 'hi.txt'");
    }
    FileWriter writeHere = new FileWriter(hi, true);
    String uling = "hi";
    writeHere.append(uling);
    writeHere.close();
}
//error catching
catch (IOException e) {
    System.out.printf("\nError. Check the file 'hi.txt'.");
}

NOTICE: Modifications at lines 7-9 .

http://docs.oracle.com/javase/7/docs/api/java/io/FileWriter.html

Answer 3

It is very important not to forget to close the writer. Well, if you do not close it, it will not be written.

writer.close().