JAVA：IO和NIO

常用IO流

• InputStream/Reader：所有输入流的基类，前者是字节输入流，后者是字符输入流
• OutputStream/Writer：所有输出流的基类，前者是字节输出流，后者是字符输出流

分类	字节输入流	字节输出流	字符输入流	字符输出流
抽象基类	InputStream	OutputStream	Reader	Writer
访问文件	FileInputStream	FileOutputStream	FileReader	FileWriter
访问数组	ByteArrayInputStream	ByteArrayOutputStream	CharArrayReader	CharArrayWriter
访问管道	PipedInputStream	PipedOutputStream	PipedReader	PipedWriter
访问字符串			StringReader	StringWriter
缓冲流	BufferedInputStream	BufferedOutputStream	BufferedReader	BufferedWriter
转换流			InputStreamReader	OutputStreamWriter
对象流	ObjectInputStream	ObjectOutputStream
抽象基类	FilterInputStream	FilterOutputStream	FilterReader	FilterWriter
打印流		PrintStream		PrintWriter
推回输入流	PushbackInputStream		PushbackReader
特殊流	DataInputStream	DateOutputStream

(粗体字标出的类代表节点流，必须与指定的物理节点关联)

IO读写文件实例

public class FileInputStreamTest {
	public static void main(String[] args) throws Exception {
		//创建字节输入流
		FileInputStream fis = new FileInputStream("mysql.ini");
		//创建字节输出流
		FileOutputStream fos = new FileOutputStream("test.txt");
		//创建缓冲数组
		byte[] bbuf = new byte[1024];
		//保存实际读取的字节数
		int hasRead = 0;
		while ((hasRead = fis.read(bbuf)) > 0) {
			System.out.println(new String(bbuf, 0, hasRead));
			fos.write(bbuf, 0, hasRead);
		}
		fis.close();
	}
}

NIO读写文件实例

public class FileChannelTest {
	public static void main(String[] args) throws Exception {
		File f = new File("mysql.ini");
		try (
				//以文件输入流创建FileChannel
				FileChannel inChannel = new FileInputStream(f).getChannel();
				//以文件输出流创建FileChannel
				FileChannel outChannel = new FileOutputStream("test3.txt").getChannel()) {
			//将FileChannel中的数据全部映射成ByteBuffer
			MappedByteBuffer buffer = inChannel.map(FileChannel.MapMode.READ_ONLY,0,f.length());
			Charset charset = Charset.forName("GBK");
			//将buffer里面的数据全部输出
			outChannel.write(buffer);
			buffer.clear();
			CharsetDecoder decoder = charset.newDecoder();
			CharBuffer charBuffer = decoder.decode(buffer);
			System.out.println(charBuffer);
		}catch(IOException e){
			e.printStackTrace();
		}
	}
}

• 文件锁:在NIO中，FileChannel的lock()/trylock()方法可以获得文件锁FileLock对象，从而锁定文件；使用release()方法释放文件锁