Java 之 IO/NIO/OKIO

BIO = blocking io

AIO = Asynchronous IO

从内存读取到写入--输出

从外部到内存 -- 输入

OutputStream //文件不存在则自动创建

 try {OutputStream outputStream = new FileOutputStream("text.txt");outputStream.write('a');outputStream.write('b');} catch (IOException e) {throw new RuntimeException(e);}

读取,写入实在内存开辟空间,然后进行读写,需要及时释放

Reader ---- BufferReader

 try (InputStream inputStream = new FileInputStream("text.txt")){ //1Reader reader = new InputStreamReader(inputStream); //2BufferedReader bufferedReader = new BufferedReader(reader);// 3,增加bufferSystem.out.println(bufferedReader.readLine());inputStream.close();} catch (IOException e) {//closethrow new RuntimeException(e);} finally {//close}

嵌套了三层

BufferRead 预先读增加性能

默认8192个字节

private static int defaultCharBufferSize = 8192;
private static int defaultExpectedLineLength = 80;

bufferedOutputStream.write 需要主动flush 或者等缓冲区 8192字节满的时候才会写入,因为有缓冲

关闭close 的时候也会自动flush

 try (OutputStream outputStream = new FileOutputStream("text.txt"); BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream)) {}//通过这种方式也会自动flush

Android copy文件 FileUtils.copy

copy文件

try (InputStream inputStream = new FileInputStream("text.txt");OutputStream outputStream = new FileOutputStream("text1.txt")) {byte[] data = new byte[1024]; //每次读的字节int read;//读取的个数while ((read = inputStream.read(data)) != -1) {
//读取是个循环过程,读多少就写入多少,如果读完就是-1
//写入字节,从起始位置到读取的数量outputStream.write(data, 0, read);}} catch (FileNotFoundException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);}

可以通过buffer 减少其交互,增加性能

  try (InputStream inputStream = new BufferedInputStream(new FileInputStream("text.txt"));OutputStream outputStream = new BufferedOutputStream(new FileOutputStream("text1.txt"))) {byte[] data = new byte[1024];int read;while ((read = inputStream.read(data)) != -1) {outputStream.write(data, 0, read);}} catch (FileNotFoundException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);}

不然每次读写交互频率较高

Socket:

 try (Socket socket = new Socket("sougou.com", 80);BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()))) {// getOutputStream 写入//getInputStream 读取writer.write("GET / HTTP/1.1\n" + "HOST: www.example.com\n\n"); //请求报文writer.flush(); //提交String message;while ((message = reader.readLine()) != null) {//读取相应内容System.out.println(message);}} catch (IOException e) {throw new RuntimeException(e);}

NIO

传统IO Stream /管道

NIO Channel/ 双向

NIO Buffer

Buffer 可以操作,强制使用

非阻塞式 //支持非阻塞式,默认阻塞式,只有网络交互时支持非阻塞式,文件交互不支持

     try {//capacity limit 上限,移动位置 一般不变//position 位置,指针位置
//r 读权限,w 写入RandomAccessFile randomAccessFile = new RandomAccessFile("text.txt","rw");FileChannel fileChannel = randomAccessFile.getChannel();ByteBuffer byteBuffer = ByteBuffer.allocate(1024); //目前不支持读取fileChannel.read(byteBuffer);//这两行等同于下面一行byteBuffer.limit(byteBuffer.position());byteBuffer.position(0);//等同于这种写法byteBuffer.flip();System.out.println();} catch (IOException e) {throw new RuntimeException(e);}

每次读完都要clear

byteBuffer.clear();

阻塞式NIO

    try {ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();serverSocketChannel.bind(new InetSocketAddress(80));SocketChannel socketChannel = serverSocketChannel.accept();//阻塞式ByteBuffer byteBuffer = ByteBuffer.allocate(1024);socketChannel.read(byteBuffer);byteBuffer.flip();System.out.println(byteBuffer);byteBuffer.clear();} catch (IOException e) {throw new RuntimeException(e);}

非阻塞式

serverSocketChannel.configureBlocking(false); //默认true 阻塞式

   try {ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();serverSocketChannel.bind(new InetSocketAddress(80));serverSocketChannel.configureBlocking(false);//非阻塞Selector selector = Selector.open();//选择器serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);//注册while (true){selector.select();//选择for (SelectionKey key : selector.selectedKeys()){if (key.isAcceptable()){SocketChannel  socketChannel = serverSocketChannel.accept();ByteBuffer byteBuffer = ByteBuffer.allocate(1024);while (socketChannel.read(byteBuffer) != -1){byteBuffer.flip();System.out.println(byteBuffer);byteBuffer.clear();}}else break;}}} catch (IOException e) {throw new RuntimeException(e);}

OKIO

基于NIO进行包装

也是基于管道 ,单向 Source 和 Sink

支持Buffer /可以对Buffer 进行操作 / 不强制使用Buff