How to Write text file Java

Question

The following code does not produce a file (I can't see the file anywhere). What is missing?

try {
    //create a temporary file
    String timeLog = new SimpleDateFormat("yyyyMMdd_HHmmss").format(
        Calendar.getInstance().getTime());
    File logFile=new File(timeLog);

    BufferedWriter writer = new BufferedWriter(new FileWriter(logFile));
    writer.write (string);

    //Close writer
    writer.close();
} catch(Exception e) {
    e.printStackTrace();
}

Answer 1

I think your expectations and reality don't match (but when do they ever ;))

Basically, where you think the file is written and where the file is actually written are not equal (hmmm, perhaps I should write an if statement ;))

public class TestWriteFile {

    public static void main(String[] args) {
        BufferedWriter writer = null;
        try {
            //create a temporary file
            String timeLog = new SimpleDateFormat("yyyyMMdd_HHmmss").format(Calendar.getInstance().getTime());
            File logFile = new File(timeLog);

            // This will output the full path where the file will be written to...
            System.out.println(logFile.getCanonicalPath());

            writer = new BufferedWriter(new FileWriter(logFile));
            writer.write("Hello world!");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                // Close the writer regardless of what happens...
                writer.close();
            } catch (Exception e) {
            }
        }
    }
}

Also note that your example will overwrite any existing files. If you want to append the text to the file you should do the following instead:

writer = new BufferedWriter(new FileWriter(logFile, true));

Answer 2

I would like to add a bit more to MadProgrammer's Answer.

In case of multiple line writing, when executing the command

writer.write(string);

one may notice that the newline characters are omitted or skipped in the written file even though they appear during debugging or if the same text is printed onto the terminal with,

System.out.println("\n");

Thus, the whole text comes as one big chunk of text which is undesirable in most cases. The newline character can be dependent on the platform, so it is better to get this character from the java system properties using

String newline = System.getProperty("line.separator");

and then using the newline variable instead of "\n". This will get the output in the way you want it.

Answer 3

In java 7 can now do

try(BufferedWriter w = ....)
{
  w.write(...);
}
catch(IOException)
{
}

and w.close will be done automatically

Answer 4

It's not creating a file because you never actually created the file. You made an object for it. Creating an instance doesn't create the file.

File newFile = new File("directory", "fileName.txt");

You can do this to make a file:

newFile.createNewFile();

You can do this to make a folder:

newFile.mkdir();

Answer 5

Using java 8 LocalDateTime and java 7 try-with statement:

public class WriteFile {

    public static void main(String[] args) {

        String timeLog = DateTimeFormatter.ofPattern("yyyyMMdd_HHmmss").format(LocalDateTime.now());
        File logFile = new File(timeLog);

        try (BufferedWriter bw = new BufferedWriter(new FileWriter(logFile))) 
        {
            System.out.println("File was written to: "  + logFile.getCanonicalPath());
            bw.write("Hello world!");
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
    }
}

Answer 6

You can try a Java Library. FileUtils, It has many functions that write to Files.

Answer 7

It does work with me. Make sure that you append ".txt" next to timeLog. I used it in a simple program opened with Netbeans and it writes the program in the main folder (where builder and src folders are).

Answer 8

The easiest way for me is just like:

            try {
                FileWriter writer = new FileWriter("C:/Your/Absolute/Path/YourFile.txt");
                writer.write("Wow, this is so easy!");
                writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

Useful tips & tricks:

• Give it a certain path:

  new FileWriter("C:/Your/Absolute/Path/YourFile.txt");

• New line

  writer.write("\r\n");

• Append lines into existing txt

  new FileWriter("log.txt");

Hope it works!