Main.java Source code

Introduction

Here is the source code for Main.java

Source

// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Locking portions of a mapped file.
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;

public class Main {
    static final int LENGTH = 0x8FFFFFF; // 128 Mb

    static FileChannel fc;

    public static void main(String[] args) throws Exception {
        fc = new RandomAccessFile("test.dat", "rw").getChannel();
        MappedByteBuffer out = fc.map(FileChannel.MapMode.READ_WRITE, 0, LENGTH);
        for (int i = 0; i < LENGTH; i++)
            out.put((byte) 'x');
        new LockAndModify(out, 0, 0 + LENGTH / 3);
        new LockAndModify(out, LENGTH / 2, LENGTH / 2 + LENGTH / 4);
    }

    private static class LockAndModify extends Thread {
        private ByteBuffer buff;
        private int start, end;

        LockAndModify(ByteBuffer mbb, int start, int end) {
            this.start = start;
            this.end = end;
            mbb.limit(end);
            mbb.position(start);
            buff = mbb.slice();
            start();
        }

        public void run() {
            try {
                FileLock fl = fc.lock(start, end, false);
                System.out.println("Locked: " + start + " to " + end);

                while (buff.position() < buff.limit() - 1) {
                    buff.put((byte) (buff.get() + 1));
                }
                fl.release();
                System.out.println("Released: " + start + " to " + end);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}