io-nio-socket步步为营（一）流基础
前沿：半路出家，自学io-nio-socket这块有些时日了，反反复复好多次，收获了很多，也记住了很多，但是好像不成系统，这次想彻底整好，不在简单的记住用法，更要用心理解背后的原理。道可道非常道，实践，写入自己的思考。start...
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一、流基础____________________________________________________________
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1、流关闭顺序
结论：只需要关闭外层流即可。
思考：因为外层流使用的是Decorator模式，最终还是底层流underlying stream。
public static String testStreamColseSequence( String name )throws Exception { FileInputStream fis = new FileInputStream( name ); // InputStreamReader(fis");默认字符集为UTF-8 Reader reader = new InputStreamReader( fis ); BufferedReader br = new BufferedReader( reader ); String header = br.readLine(); br.close(); //设置断点，观察varibales，fis,reader.lock,br.lock.lock均已关闭 // 调用fis, 报Exception in thread "main" java.io.IOException: Stream Closed System.out.println( "fis.read()=" + fis.read() ); return header; }?
2、io与nio比较
结论：单纯复制byte流方面，io甚至比nio快些，因为从1.4开始io用nio重新实现了，按块读取，但是
nio多个线程复制一个连接的优势，io-socket是无法获得的。
思考：需要操作系统级别的I/O，unix网络编程实践。有待提升
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import java.io.FileInputStream;import java.io.FileOutputStream;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;/** * 测试数据：2个完全一样的的视频,101M的mp4 * iioCopy=327,nioCopy=422,因为从1.4开始io用nio重写了 ，从FileChannel fc1 = in.getChannel();即可看出端倪 * 面向流 的 I/O系统一次一个字节地处 理数据。NIO按块处理数据比按(流式的)字节处理数据要快得多，但缺少I/O的简单优雅 * @author timeriver.wang * @date 2012-12-07 9:37:22 AM */public class IOpkNIOCopy { private static int LEN_8K = 8192; public static void main( String[] args ) throws Exception { ioCopy( "e:/work/1/1.MP4", "e:/work/2/1.MP4" ); nioCopy( "e:/work/1/2.MP4", "e:/work/2/2.MP4" ); } public static void ioCopy( String name1, String name2 ) throws Exception { long start = System.currentTimeMillis(); FileInputStream fis = new FileInputStream( name1 ); FileOutputStream fos = new FileOutputStream( name2 ); byte[] buf = new byte[LEN_8K]; while ( true ) { int n = fis.read( buf ); if ( n == -1 ) { break; } fos.write( buf, 0, n ); // 这行代码会使复制的视频变花屏。 // fos.write(99); } fis.close(); fos.close(); long end = System.currentTimeMillis(); long time = end - start; System.out.println( "iioCopy=" + time ); } public static void nioCopy( String name1, String name2 ) throws Exception { long start = System.currentTimeMillis(); FileInputStream in = new FileInputStream( name1 ); FileOutputStream out = new FileOutputStream( name2 ); // Since:1.4,java从1.4开始提升性能 // Returns the unique FileChannel object associated with this file input stream. FileChannel fc1 = in.getChannel(); FileChannel fc2 = out.getChannel(); ByteBuffer bb = ByteBuffer.allocate( LEN_8K ); while ( true ) { bb.clear(); int n = fc1.read( bb ); if ( n == -1 ) { break; } bb.flip(); fc2.write( bb ); } fc1.close(); fc2.close(); long end = System.currentTimeMillis(); long time = end - start; System.out.println( "nioCopy=" + time ); }}?3、最基础的InputStream,OutputStream才是最终要的，源代码显示都是，单字节的read()，归根结缔。只是read是抽象的，但是read(byte[])不是，代码技巧。reader也是。
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RandomAccessFile implements DataOutput, DataInput, Closeable
ByteArrayInputStream extends InputStream
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public abstract class InputStream implements Closeable { private static final int MAX_SKIP_BUFFER_SIZE = 2048;// 各种read方法，各种上层input流最终都依赖这个read,体味编程之美。 public abstract int read() throws IOException; public int read(byte b[]) throws IOException { return read(b, 0, b.length); } public int read(byte b[], int off, int len) throws IOException { int c = read(); } public long skip(long n) throws IOException { nr = read(skipBuffer, 0, (int)Math.min(size, remaining)); } public int available() throws IOException { return 0; } public void close() throws IOException {}// synchronized. public synchronized void mark(int readlimit) {} public synchronized void reset() throws IOException { throw new IOException("mark/reset not supported"); } public boolean markSupported() {return false;}}?FileInputStream extends InputStream
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public class FileInputStream extends InputStream{ public native int read() throws IOException; //不再调用read()了，按块读，不再按byte读取了？ private native int readBytes(byte b[], int off, int len) throws IOException; public int read(byte b[], int off, int len) throws IOException { return readBytes(b, off, len); } //也重写父类的skip为natvie方法了，不再调用read()了， public native long skip(long n) throws IOException; //since 1.4 public FileChannel getChannel() { synchronized (this) {FileChannelImpl.open...} }}?SocketInputStream extends FileInputStream
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private native int socketRead0(FileDescriptor fd,byte b[], int off, int len,int timeout)?
4、read()返回[0-255]的int,把有符号的byte数值，转换成了无符号的int数值。可以用来判断是否EOF流结束了与否
，验证代码如下
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/** * @author timeriver.wang * @date 2012-12-10 10:45:17 AM */public class Test { public static void main( String[] args ) throws Exception{ String filePath = "d:/12.txt"; writeFile(filePath); readFile( filePath ); } public static void writeFile(String filePath) throws IOException{ ByteBuffer bb = ByteBuffer.allocate( 20 ); bb.putChar( 'a' ); bb.putInt( -255 ); bb.putShort((short) -255 ); bb.putChar( 'b' ); bb.putChar( 'c' ); FileOutputStream fos = new FileOutputStream(filePath); fos.write( bb.array()); } public static void readFile(String filePath) throws IOException{ FileInputStream fis = new FileInputStream(filePath); ByteBuffer readbuff = ByteBuffer.allocate( 20 ); //写入的byte -1,read读取的是255,即无符号的byte数值。 int i = fis.read(); while(i != -1){ readbuff.put( (byte)i); System.out.println(i); i = fis.read(); } System.out.println(readbuff); }}