Java Nio File channel code including write/read/copy/lock/map

NioFile.java

import org.junit.Test;

import java.io.ByteArrayOutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;

public class NioFile {
    @Test
    public void write() {
        try (
                RandomAccessFile file = new RandomAccessFile("test.out", "rw");
                FileChannel channel = file.getChannel()
        ) {
            for (int i = 0; i < 1000; i++) {
                final ByteBuffer wrap = ByteBuffer.wrap("fork you\n".getBytes());
                channel.write(wrap);
            }

            channel.force(true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void read() {
        try (
                RandomAccessFile file = new RandomAccessFile("test.out", "rw");
                FileChannel channel = file.getChannel();
                final ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream()
        ) {
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            while (channel.read(byteBuffer) > 0) {
                byteOutputStream.write(byteBuffer.array(), 0, byteBuffer.position());
                byteBuffer.clear();
            }
            System.out.println(new String(byteOutputStream.toByteArray()).length());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void copy() {
        try (
                RandomAccessFile file = new RandomAccessFile("test.out", "r");
                RandomAccessFile file2 = new RandomAccessFile("test.out3", "rw");
                FileChannel channel = file.getChannel();
                FileChannel channel2 = file2.getChannel();
        ) {
            channel2.truncate(0);
            ByteBuffer byteBuffer = ByteBuffer.allocate(16);
            while (channel.read(byteBuffer) > 0) {
                byteBuffer.flip();
                channel2.write(byteBuffer);
                byteBuffer.flip();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 进程间： lock()将block,tryLock()返回null
     * 线程间： lock()将block,tryLock()抛出异常
     */
    @Test
    public void lock() {
        try (
                RandomAccessFile file2 = new RandomAccessFile("test.out3", "rw");
                FileChannel channel2 = file2.getChannel();
                final FileLock lock = channel2.lock()
        ) {
            Thread another = new Thread(() -> {
                tryLock();
            });
            another.start();
            Thread.sleep(15*1000);
            System.out.println("lock released");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void tryLock() {
        try (
                RandomAccessFile file2 = new RandomAccessFile("test.out3", "rw");
                FileChannel channel2 = file2.getChannel();
                final FileLock lock = channel2.tryLock();
        ) {
            System.out.println(lock);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void map() {
        try (
                RandomAccessFile file2 = new RandomAccessFile("test.out3", "rw");
                FileChannel channel2 = file2.getChannel();
        ) {
            final MappedByteBuffer map = channel2.map(FileChannel.MapMode.READ_WRITE, 0, 100);
            //可以做多线程分段文件下载
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}