MappedByteBuffer writing to file not working

Question

I am having hard time understanding the read write with MappedByteBuffer. Here is the class I have that reads the content of a local file and suppose to reverse its content. I am using java version 8.

public class MappedByteBufferExample {
public static void main(String[] args) {
    try (RandomAccessFile file = new RandomAccessFile("resources\\MappedByteBufferExample.txt", "rw");
            FileChannel fileChannel = file.getChannel();) {
        long size = fileChannel.size();
        MappedByteBuffer mappedBuffer = fileChannel.map(MapMode.READ_WRITE, 0, size);

        System.out.println("Text from File : -----");
        while (mappedBuffer.remaining() > 0) {
            System.out.print((char) mappedBuffer.get());
        }
        System.out.println("\n");

        for (int index = 0; index < (mappedBuffer.limit() / 2); index++) {
            byte b1 = mappedBuffer.get(index);
            byte b2 = mappedBuffer.get(mappedBuffer.limit() - index - 1);
            mappedBuffer.put(index, b2);
            mappedBuffer.put(mappedBuffer.limit() - index - 1, b1);
        }
        //mappedBuffer.force();  I tried with this but no change in result.
        //mappedBuffer.load(); I tried with this but no change in result.
        mappedBuffer.load();
        mappedBuffer.flip();
        System.out.println("Text Reversed : -----");
        while (mappedBuffer.remaining() > 0) {
            System.out.print((char) mappedBuffer.get());
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}}

The content of the file is - Roses are Red!
On executing this file output to the console is:

Text from File : -----

Roses are Red!

Text Reversed : -----

!deR era sesoR

But the content of the file is unchanged. On executing this program on second time, the output to the console is:

Text from File : -----

!deR era sesoR

Text Reversed : -----

Roses are Red!

The content of the file is still unchanged. I tried load() and force() methods one at a time and both, but no change in the result Here are my questions:

1) Why the content of the local file is not changed?

2) What changes does this program need to make the data to be written to the file?

3) Why/How the MappedByteBuffer has read reversed text on second iteration, though the file content is not reversed?

Answer 1

The content of the file IS changed. Usual editors (like notepad++ or eclipse) do not remark the change because the file datetime is not changed by using RandomAccessFile. But if you really reload the file manually after the run you should see the changes.