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Best way to write String to file using java nio

stackoverflow.com › questions › 7366266 › best-way-to-write-string-to-file-using-java-nio

`Files.writeString`

In Java 11+, there is a convenient method to write strings. Call java.nio.file.Files.writeString:

Files.writeString(
    Paths.get(file.toURI()),   // Path to file.
    "My string to save",       // String to write.
    StandardCharsets.UTF_8     // Character encoding to use in writing file.
);

We can also customize the writing with:

Files.writeString(Paths.get(file.toURI()), 
                  "My string to save", 
                   StandardCharsets.UTF_8,
                   StandardOpenOption.CREATE,
                   StandardOpenOption.TRUNCATE_EXISTING);

ORIGINAL ANSWER:

There is a one-line solution, using Java nio:

java.nio.file.Files.write(Paths.get(file.toURI()), 
                          "My string to save".getBytes(StandardCharsets.UTF_8),
                          StandardOpenOption.CREATE,
                          StandardOpenOption.TRUNCATE_EXISTING);

I have not benchmarked this solution with the others, but using the built-in implementation for open-write-close file should be fast and the code is quite small.

Answer from Roberto on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 7366266 › best-way-to-write-string-to-file-using-java-nio

Best way to write String to file using java nio - Stack Overflow

`Files.writeString`

In Java 11+, there is a convenient method to write strings. Call java.nio.file.Files.writeString:

Files.writeString(
    Paths.get(file.toURI()),   // Path to file.
    "My string to save",       // String to write.
    StandardCharsets.UTF_8     // Character encoding to use in writing file.
);

We can also customize the writing with:

Files.writeString(Paths.get(file.toURI()), 
                  "My string to save", 
                   StandardCharsets.UTF_8,
                   StandardOpenOption.CREATE,
                   StandardOpenOption.TRUNCATE_EXISTING);

ORIGINAL ANSWER:

There is a one-line solution, using Java nio:

java.nio.file.Files.write(Paths.get(file.toURI()), 
                          "My string to save".getBytes(StandardCharsets.UTF_8),
                          StandardOpenOption.CREATE,
                          StandardOpenOption.TRUNCATE_EXISTING);

I have not benchmarked this solution with the others, but using the built-in implementation for open-write-close file should be fast and the code is quite small.

2 of 5

I don't think you will be able to get a strict answer without benchmarking your software. NIO may speed up the application significantly under the right conditions, but it may also make things slower. Here are some points:

Do you really need strings? If you store and receive bytes from you database you can avoid string allocation and encoding costs all together.
Do you really need rewind and flip? Seems like you are creating a new buffer for every string and just writing it to the channel. (If you go the NIO way, benchmark strategies that reuse the buffers instead of wrapping / discarding, I think they will do better).
Keep in mind that wrap and allocateDirect may produce quite different buffers. Benchmark both to grasp the trade-offs. With direct allocation, be sure to reuse the same buffer in order to achieve the best performance.
And the most important thing is: Be sure to compare NIO with BufferedOutputStream and/or BufferedWritter approaches (use a intermediate byte[] or char[] buffer with a reasonable size as well). I've seen many, many, many people discovering that NIO is no silver bullet.

If you fancy some bleeding edge... Back to IO Trails for some NIO2 :D.

And here is a interesting benchmark about file copying using different strategies. I know it is a different problem, but I think most of the facts and author conclusions also apply to your problem.

Cheers,

UPDATE 1:

Since @EJP tiped me that direct buffers wouldn't be efficient for this problem, I benchmark it myself and ended up with a nice NIO solution using nemory-mapped files. In my Macbook running OS X Lion this beats BufferedOutputStream by a solid margin. but keep in mind that this might be OS / Hardware / VM specific:

public void writeToFileNIOWay2(File file) throws IOException {
    final int numberOfIterations = 1000000;
    final String messageToWrite = "This is a test üüüüüüööööö";
    final byte[] messageBytes = messageToWrite.
            getBytes(Charset.forName("ISO-8859-1"));
    final long appendSize = numberOfIterations * messageBytes.length;
    final RandomAccessFile raf = new RandomAccessFile(file, "rw");
    raf.seek(raf.length());
    final FileChannel fc = raf.getChannel();
    final MappedByteBuffer mbf = fc.map(FileChannel.MapMode.READ_WRITE, fc.
            position(), appendSize);
    fc.close();
    for (int i = 1; i < numberOfIterations; i++) {
        mbf.put(messageBytes);
    }
}

I admit that I cheated a little by calculating the total size to append (around 26 MB) beforehand. This may not be possible for several real world scenarios. Still, you can always use a "big enough appending size for the operations and later truncate the file.

UPDATE 2 (2019):

To anyone looking for a modern (as in, Java 11+) solution to the problem, I would follow @DodgyCodeException's advice and use java.nio.file.Files.writeString:

String fileName = "/xyz/test.txt";
String messageToWrite = "My long string";
Files.writeString(Paths.get(fileName), messageToWrite, StandardCharsets.ISO_8859_1);

Medium

medium.com › @vusal.guliyev.313 › writing-files-with-nio-and-io-in-java-bc60b06a413a

Writing Files with NIO and IO in Java | by Vusal Guliyev | Medium

February 9, 2024 - In this NIO example, the Files.write() method is used to write data to a file. The file path, data to be written (converted to bytes), and options such as CREATE to create the file if it doesn’t exist are specified.

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