Memory map file mappedbytebuffer

The DirectByteBuffer mentioned in the previous article inherits from MappedByteBuffer

The definition of MappedByteBuffer:

A direct byte buffer whose content is a memory-mapped region of a file.

Direct cache, the content is a memory mapped file.

Create a test class

public class NioTest9 {
    public static void main(String[] args) throws Exception {
        RandomAccessFile randomAccessFile = new RandomAccessFile("NioTest9.txt","rw");
        FileChannel fileChannel = randomAccessFile.getChannel();
        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0,5);
        mappedByteBuffer.put(0,(byte)‘a’);
        mappedByteBuffer.put(3,(byte)‘b’);

        randomAccessFile.close();
    }
}

　Create NioTest9.tex file

　Run the program and open it with Notepad

The operation is off-heap memory, off-heap memory Writing to the file is controlled by the operating system.

public class NioTest9 {
    public static void main(String[] args) throws Exception {
        RandomAccessFile randomAccessFile = new RandomAccessFile("NioTest9.txt","rw");
        FileChannel fileChannel = randomAccessFile.getChannel();
        MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0,5);
        mappedByteBuffer.put(0,(byte)‘a’);
        mappedByteBuffer.put(3,(byte)‘b’);

        randomAccessFile.close();
    }
}