1 import java.io.FileInputStream;  2 import java.io.FileOutputStream;  3 import java.io.IOException;  4 import java.io.RandomAccessFile;  5 import java.nio.ByteBuffer;  6 import java.nio.CharBuffer;  7 import java.nio.MappedByteBuffer;  8 import java.nio.channels.FileChannel;  9 import java.nio.channels.FileChannel.MapMode; 10 import java.nio.charset.CharacterCodingException; 11 import java.nio.charset.Charset; 12 import java.nio.charset.CharsetDecoder; 13 import java.nio.charset.CharsetEncoder; 14 import java.nio.file.Paths; 15 import java.nio.file.StandardOpenOption; 16 import java.util.Map; 17 import java.util.Map.Entry; 18 import java.util.Set; 19  20 import org.junit.Test; 21  22 /* 23  * 一、通道（Channel）：用于源节点与目标节点的连接。在 Java NIO 中负责缓冲区中数据的传输。Channel 本身不存储数据，因此需要配合缓冲区进行传输。 24  *  25  * 二、通道的主要实现类 26  *     java.nio.channels.Channel 接口： 27  *         |--FileChannel 28  *         |--SocketChannel 29  *         |--ServerSocketChannel 30  *         |--DatagramChannel 31  *  32  * 三、获取通道 33  * 1. Java 针对支持通道的类提供了 getChannel() 方法 34  *         本地 IO： 35  *         FileInputStream/FileOutputStream 36  *         RandomAccessFile 37  *  38  *         网络IO： 39  *         Socket 40  *         ServerSocket 41  *         DatagramSocket 42  *          43  * 2. 在 JDK 1.7 中的 NIO.2 针对各个通道提供了静态方法 open() 44  * 3. 在 JDK 1.7 中的 NIO.2 的 Files 工具类的 newByteChannel() 45  *  46  * 四、通道之间的数据传输 47  * transferFrom() 48  * transferTo() 49  *  50  * 五、分散(Scatter)与聚集(Gather) 51  * 分散读取（Scattering Reads）：将通道中的数据分散到多个缓冲区中 52  * 聚集写入（Gathering Writes）：将多个缓冲区中的数据聚集到通道中 53  *  54  * 六、字符集：Charset 55  * 编码：字符串 -> 字节数组 56  * 解码：字节数组  -> 字符串 57  *  58  */ 59 public class TestChannel { 60      61     //字符集 62     @Test 63     public void test6() throws IOException{ 64         Charset cs1 = Charset.forName("GBK"); 65          66         //获取编码器 67         CharsetEncoder ce = cs1.newEncoder(); 68          69         //获取解码器 70         CharsetDecoder cd = cs1.newDecoder(); 71          72         CharBuffer cBuf = CharBuffer.allocate(1024); 73         cBuf.put("好好学习天天向上！"); 74         cBuf.flip(); 75          76         //编码 77         ByteBuffer bBuf = ce.encode(cBuf); 78          79         for (int i = 0; i < 12; i++) { 80             System.out.println(bBuf.get()); 81         } 82          83         //解码 84         bBuf.flip(); 85         CharBuffer cBuf2 = cd.decode(bBuf); 86         System.out.println(cBuf2.toString()); 87          88         System.out.println("------------------------------------------------------"); 89          90         Charset cs2 = Charset.forName("GBK"); 91         bBuf.flip(); 92         CharBuffer cBuf3 = cs2.decode(bBuf); 93         System.out.println(cBuf3.toString()); 94     } 95      96     @Test 97     public void test5(){ 98         Map
     
       map = Charset.availableCharsets(); 99         100         Set
      
       
        > set = map.entrySet();101         102         for (Entry
        
          entry : set) {103             System.out.println(entry.getKey() + "=" + entry.getValue());104         }105     }106     107     //分散和聚集108     @Test109     public void test4() throws IOException{110         RandomAccessFile raf1 = new RandomAccessFile("1.txt", "rw");111         112         //1. 获取通道113         FileChannel channel1 = raf1.getChannel();114         115         //2. 分配指定大小的缓冲区116         ByteBuffer buf1 = ByteBuffer.allocate(100);117         ByteBuffer buf2 = ByteBuffer.allocate(1024);118         119         //3. 分散读取120         ByteBuffer[] bufs = {buf1, buf2};121         channel1.read(bufs);122         123         for (ByteBuffer byteBuffer : bufs) {124             byteBuffer.flip();125         }126         127         System.out.println(new String(bufs[0].array(), 0, bufs[0].limit()));128         System.out.println("-----------------");129         System.out.println(new String(bufs[1].array(), 0, bufs[1].limit()));130         131         //4. 聚集写入132         RandomAccessFile raf2 = new RandomAccessFile("2.txt", "rw");133         FileChannel channel2 = raf2.getChannel();134         135         channel2.write(bufs);136     }137     138     //通道之间的数据传输(直接缓冲区)139     @Test140     public void test3() throws IOException{141         FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);142         FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);143         144 //        inChannel.transferTo(0, inChannel.size(), outChannel);145         outChannel.transferFrom(inChannel, 0, inChannel.size());146         147         inChannel.close();148         outChannel.close();149     }150     151     //使用直接缓冲区完成文件的复制(内存映射文件)152     @Test153     public void test2() throws IOException{
    //2127-1902-1777154         long start = System.currentTimeMillis();155         156         FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);157         FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);158         159         //内存映射文件160         MappedByteBuffer inMappedBuf = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());161         MappedByteBuffer outMappedBuf = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());162         163         //直接对缓冲区进行数据的读写操作164         byte[] dst = new byte[inMappedBuf.limit()];165         inMappedBuf.get(dst);166         outMappedBuf.put(dst);167         168         inChannel.close();169         outChannel.close();170         171         long end = System.currentTimeMillis();172         System.out.println("耗费时间为：" + (end - start));173     }174     175     //利用通道完成文件的复制（非直接缓冲区）176     @Test177     public void test1(){
    //10874-10953178         long start = System.currentTimeMillis();179         180         FileInputStream fis = null;181         FileOutputStream fos = null;182         //①获取通道183         FileChannel inChannel = null;184         FileChannel outChannel = null;185         try {186             fis = new FileInputStream("d:/1.mkv");187             fos = new FileOutputStream("d:/2.mkv");188             189             inChannel = fis.getChannel();190             outChannel = fos.getChannel();191             192             //②分配指定大小的缓冲区193             ByteBuffer buf = ByteBuffer.allocate(1024);194             195             //③将通道中的数据存入缓冲区中196             while(inChannel.read(buf) != -1){197                 buf.flip(); //切换读取数据的模式198                 //④将缓冲区中的数据写入通道中199                 outChannel.write(buf);200                 buf.clear(); //清空缓冲区201             }202         } catch (IOException e) {203             e.printStackTrace();204         } finally {205             if(outChannel != null){206                 try {207                     outChannel.close();208                 } catch (IOException e) {209                     e.printStackTrace();210                 }211             }212             213             if(inChannel != null){214                 try {215                     inChannel.close();216                 } catch (IOException e) {217                     e.printStackTrace();218                 }219             }220             221             if(fos != null){222                 try {223                     fos.close();224                 } catch (IOException e) {225                     e.printStackTrace();226                 }227             }228             229             if(fis != null){230                 try {231                     fis.close();232                 } catch (IOException e) {233                     e.printStackTrace();234                 }235             }236         }237         238         long end = System.currentTimeMillis();239         System.out.println("耗费时间为：" + (end - start));240         241     }242 243 }