Java编程思想：文件加锁

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
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;
import java.util.concurrent.TimeUnit;

public class Test {
    public static void main(String[] args){
//        FileLocking.test();
        LockingmappedFiles.test();

    }
}

class FileLocking {
    public static void test() {
        try {
            FileOutputStream out = new FileOutputStream("temp.tmp");
            FileLock fl = out.getChannel().tryLock();
            if (fl != null) {
                System.out.println("Locked File");
                TimeUnit.SECONDS.sleep(100);
                fl.release();
                System.out.println("Released Lock");
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

class LockingmappedFiles {
    private static final int LENGTH = 0X8000000; //128MB
    private static FileChannel fc;

    public static void test() {
        try {
            fc = new RandomAccessFile("test.data", "rw")
                    .getChannel();

            MappedByteBuffer out = fc
                    .map(FileChannel.MapMode.READ_WRITE, 0, LENGTH);

            for (int i = 0; i < LENGTH; i++) {
                out.put((byte)'c');
            }

            new LockAndModify(out, 0, 0 + LENGTH / 3);
            new LockAndModify(out, LENGTH / 2, LENGTH / 2 + LENGTH / 4);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

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

        public LockAndModify(ByteBuffer bb, int start, int end) {
            this.start=start;
            this.end=end;

            //这段写法学习下
            bb.limit(end);
            bb.position(start);
            buff = bb.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) {
                e.printStackTrace();
            }
        }
    }

}