NIO全文

Pipe

两个线程之间的单向数据连接，从source通道读取和sink通道写入

//获取通道
Pipe pipe = Pipe.open();
//写入
Pipe.SinkChannel sink = pipe.sink();
ByteBuffer bbSink = ByteBuffer.allocate(1024);
bbSink.put("PipeDemo".getBytes());
bbSink.flip();
sink.write(bbSink);
//读取
Pipe.SourceChannel source = pipe.source();
ByteBuffer bbSource = ByteBuffer.allocate(1024);
int len = source.read(bbSource);
System.out.println(new String(bbSource.array(), 0, len));
source.close();
sink.close();

两个线程的案例

Pipe pipe = Pipe.open();
new Thread(() -> {
    Pipe.SourceChannel source = pipe.source();
    ByteBuffer bb = ByteBuffer.allocate(1024);
    bb.clear();
    try {
        //阻塞在这里，等待sink端写入
        int len = source.read(bb);
        if (len != -1) {
            bb.flip();
            System.out.println(new String(bb.array(), 0, len));
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    System.out.println(Thread.currentThread().getName() + " - finished");
},"B").start();
new Thread(() -> {
    Pipe.SinkChannel sink = pipe.sink();
    ByteBuffer bb = ByteBuffer.allocate(1024);
    bb.put(Thread.currentThread().getName().getBytes());
    bb.flip();
    try {
        TimeUnit.SECONDS.sleep(1);
        sink.write(bb);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            sink.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    System.out.println(Thread.currentThread().getName() + " - finished");
}, "A").start();

FileLock

文件锁，同一个时间，只能有一个程序修改此文件
进程级别，解决多个进程并发访问、修改同一个文件的问题；同一个进程内的多个线程，可以同时访问，修改文件
进程对文件不能重复加锁
锁释放

调用release()

关闭对应的FileChannel对象

当前JVM退出

分类

排它锁，独占锁，对文件加锁后，其他进程不能读写此文件，直到该进程释放锁

共享锁，其他进程只能读此文件

lock与tyrlock

lock，阻塞式的，如果未获取到文件锁，会一直阻塞当前线程

非阻塞式，尝试获取文件锁，成功返回锁对象，失败返回null

实际上是一种设计思想，只有获取锁之后才能进行处理

String pathName = "/Users/mzx/Desktop/java/nio/test4.txt";
String input = Thread.currentThread().getName();
Path path = Paths.get(pathName);
ByteBuffer bb = ByteBuffer.allocate(1024);
FileChannel fc = FileChannel.open(path, StandardOpenOption.READ, StandardOpenOption.WRITE);
//加锁，如果是独占锁，其他进程不能获得锁；如果是共享锁，就可以获得
FileLock lock = fc.lock(0, Long.MAX_VALUE, true);
fc.position(fc.size() - 1);
fc.write(ByteBuffer.wrap(input.getBytes()));
//是否是共享锁
System.out.println(lock.isShared());
//读
fc.position(0);
int len = fc.read(bb);
System.out.println(len);
bb.flip();
System.out.println(new String(bb.array(), 0, len));
TimeUnit.SECONDS.sleep(300);

Path

获取

String pathName = "/Users/mzx/Desktop/java/nio/test4.txt";
//创建决定路径
Path path = Paths.get(pathName);
System.out.println(path);
//创建相对路径，路径拼接
Path path1 = Paths.get("/Users/mzx/Desktop/java", "nio/test4.txt");
System.out.println(path1);

//sout
/Users/mzx/Desktop/java/nio/test4.txt
/Users/mzx/Desktop/java/nio/test4.txt

标准化

//..代表Desktop的上一层
String pathName1 = "/Users/mzx/Desktop/../java/nio/test4.txt";
Path path2 = Paths.get(pathName1);
System.out.println(path2);
Path path3 = path2.normalize();
System.out.println(path3);

//sout
/Users/mzx/Desktop/../java/nio/test4.txt
/Users/mzx/java/nio/test4.txt

Files

//新建目录，目录存在或者不存在父目录，抛出异常；
Path path = Paths.get("/Users/mzx/Desktop/java/nio/test");
Files.createDirectory(path);
//递归创建
Files.createDirectories(Paths.get("/Users/mzx/Desktop/java/nio/test1/test"));

文件复制

Path from = Paths.get("/Users/mzx/Desktop/java/nio/test1.txt");
Path to = Paths.get("/Users/mzx/Desktop/java/nio/test/test10.txt");
Files.copy(from,to);
//覆盖
Files.copy(from,to, StandardCopyOption.REPLACE_EXISTING);

移动和重命名

Path from = Paths.get("/Users/mzx/Desktop/java/nio/test/test101.txt");
Path to = Paths.get("/Users/mzx/Desktop/java/nio/test/test10.txt");
//可以进行重命名，文件名与to相同，会异常，可以进行覆盖
Files.move(from, to, StandardCopyOption.REPLACE_EXISTING);

删除

Path path = Paths.get("/Users/mzx/Desktop/java/nio/test/test10.txt");
Files.delete(path);
Files.deleteIfExists(path);

Path root = Paths.get("/Users/mzx/Desktop/java/nio");
//找文件
String fileToFind = File.separator + "test4.txt";
Files.walkFileTree(root, new SimpleFileVisitor<Path>() {
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        String fileString = file.toAbsolutePath().toString();
        if (fileString.endsWith(fileToFind)) {
            System.out.println("success - " + file.toAbsolutePath());
            return FileVisitResult.TERMINATE;
        }
        System.out.println(file.toAbsolutePath());
        return FileVisitResult.CONTINUE;
    }
});

Java-第十七部分-NIO-Pipe、FileLock、Path和Files

NIO全文

Pipe

两个线程的案例

FileLock

Path

Files