1 package java.io; 2  3 import java.io.*; 4  5 public class PipedOutputStream extends OutputStream { 6  7     // 与PipedOutputStream通信的PipedInputStream对象 8     private PipedInputStream sink; 9 10     // 构造函数，指定配对的PipedInputStream11     public PipedOutputStream(PipedInputStream snk)  throws IOException {12         connect(snk);13     }14 15     // 构造函数16     public PipedOutputStream() {17     }18 19     // 将“管道输出流” 和 “管道输入流”连接。20     public synchronized void connect(PipedInputStream snk) throws IOException {21         if (snk == null) {22             throw new NullPointerException();23         } else if (sink != null || snk.connected) {24             throw new IOException("Already connected");25         }26         // 设置“管道输入流”27         sink = snk;28         // 初始化“管道输入流”的读写位置29         // int是PipedInputStream中定义的，代表“管道输入流”的读写位置30         snk.in = -1;31         // 初始化“管道输出流”的读写位置。32         // out是PipedInputStream中定义的，代表“管道输出流”的读写位置33         snk.out = 0;34         // 设置“管道输入流”和“管道输出流”为已连接状态35         // connected是PipedInputStream中定义的，用于表示“管道输入流与管道输出流”是否已经连接36         snk.connected = true;37     }38 39     // 将int类型b写入“管道输出流”中。40     // 将b写入“管道输出流”之后，它会将b传输给“管道输入流”41     public void write(int b)  throws IOException {42         if (sink == null) {43             throw new IOException("Pipe not connected");44         }45         sink.receive(b);46     }47 48     // 将字节数组b写入“管道输出流”中。49     // 将数组b写入“管道输出流”之后，它会将其传输给“管道输入流”50     public void write(byte b[], int off, int len) throws IOException {51         if (sink == null) {52             throw new IOException("Pipe not connected");53         } else if (b == null) {54             throw new NullPointerException();55         } else if ((off < 0) || (off > b.length) || (len < 0) ||56                    ((off + len) > b.length) || ((off + len) < 0)) {57             throw new IndexOutOfBoundsException();58         } else if (len == 0) {59             return;60         }61         // “管道输入流”接收数据62         sink.receive(b, off, len);63     }64 65     // 清空“管道输出流”。66     // 这里会调用“管道输入流”的notifyAll()；67     // 目的是让“管道输入流”放弃对当前资源的占有，让其它的等待线程(等待读取管道输出流的线程)读取“管道输出流”的值。68     public synchronized void flush() throws IOException {69         if (sink != null) {70             synchronized (sink) {71                 sink.notifyAll();72             }73         }74     }75 76     // 关闭“管道输出流”。77     // 关闭之后，会调用receivedLast()通知“管道输入流”它已经关闭。78     public void close()  throws IOException {79         if (sink != null) {80             sink.receivedLast();81         }82     }83 }

  1 package java.io;  2   3 public class PipedInputStream extends InputStream {  4     // “管道输出流”是否关闭的标记  5     boolean closedByWriter = false;  6     // “管道输入流”是否关闭的标记  7     volatile boolean closedByReader = false;  8     // “管道输入流”与“管道输出流”是否连接的标记  9     // 它在PipedOutputStream的connect()连接函数中被设置为true 10     boolean connected = false; 11  12     Thread readSide;    // 读取“管道”数据的线程 13     Thread writeSide;    // 向“管道”写入数据的线程 14  15     // “管道”的默认大小 16     private static final int DEFAULT_PIPE_SIZE = 1024; 17  18     protected static final int PIPE_SIZE = DEFAULT_PIPE_SIZE; 19  20     // 缓冲区 21     protected byte buffer[]; 22  23     //下一个写入字节的位置。in==out代表满，说明“写入的数据”全部被读取了。 24     protected int in = -1; 25     //下一个读取字节的位置。in==out代表满，说明“写入的数据”全部被读取了。 26     protected int out = 0; 27  28     // 构造函数：指定与“管道输入流”关联的“管道输出流” 29     public PipedInputStream(PipedOutputStream src) throws IOException { 30         this(src, DEFAULT_PIPE_SIZE); 31     } 32  33     // 构造函数：指定与“管道输入流”关联的“管道输出流”，以及“缓冲区大小” 34     public PipedInputStream(PipedOutputStream src, int pipeSize) 35             throws IOException { 36          initPipe(pipeSize); 37          connect(src); 38     } 39  40     // 构造函数：默认缓冲区大小是1024字节 41     public PipedInputStream() { 42         initPipe(DEFAULT_PIPE_SIZE); 43     } 44  45     // 构造函数：指定缓冲区大小是pipeSize 46     public PipedInputStream(int pipeSize) { 47         initPipe(pipeSize); 48     } 49  50     // 初始化“管道”：新建缓冲区大小 51     private void initPipe(int pipeSize) { 52          if (pipeSize <= 0) { 53             throw new IllegalArgumentException("Pipe Size <= 0"); 54          } 55          buffer = new byte[pipeSize]; 56     } 57  58     // 将“管道输入流”和“管道输出流”绑定。 59     // 实际上，这里调用的是PipedOutputStream的connect()函数 60     public void connect(PipedOutputStream src) throws IOException { 61         src.connect(this); 62     } 63  64     // 接收int类型的数据b。 65     // 它只会在PipedOutputStream的write(int b)中会被调用 66     protected synchronized void receive(int b) throws IOException { 67         // 检查管道状态 68         checkStateForReceive(); 69         // 获取“写入管道”的线程 70         writeSide = Thread.currentThread(); 71         // 若“写入管道”的数据正好全部被读取完，则等待。 72         if (in == out) 73             awaitSpace(); 74         if (in < 0) { 75             in = 0; 76             out = 0; 77         } 78         // 将b保存到缓冲区 79         buffer[in++] = (byte)(b & 0xFF); 80         if (in >= buffer.length) { 81             in = 0; 82         } 83     } 84  85     // 接收字节数组b。 86     synchronized void receive(byte b[], int off, int len)  throws IOException { 87         // 检查管道状态 88         checkStateForReceive(); 89         // 获取“写入管道”的线程 90         writeSide = Thread.currentThread(); 91         int bytesToTransfer = len; 92         while (bytesToTransfer > 0) { 93             // 若“写入管道”的数据正好全部被读取完，则等待。 94             if (in == out) 95                 awaitSpace(); 96             int nextTransferAmount = 0; 97             // 如果“管道中被读取的数据，少于写入管道的数据”； 98             // 则设置nextTransferAmount=“buffer.length - in” 99             if (out < in) {100                 nextTransferAmount = buffer.length - in;101             } else if (in < out) { // 如果“管道中被读取的数据，大于/等于写入管道的数据”，则执行后面的操作102                 // 若in==-1(即管道的写入数据等于被读取数据)，此时nextTransferAmount = buffer.length - in;103                 // 否则，nextTransferAmount = out - in;104                 if (in == -1) {105                     in = out = 0;106                     nextTransferAmount = buffer.length - in;107                 } else {108                     nextTransferAmount = out - in;109                 }110             }111             if (nextTransferAmount > bytesToTransfer)112                 nextTransferAmount = bytesToTransfer;113             // assert断言的作用是，若nextTransferAmount <= 0，则终止程序。114             assert(nextTransferAmount > 0);115             // 将数据写入到缓冲中116             System.arraycopy(b, off, buffer, in, nextTransferAmount);117             bytesToTransfer -= nextTransferAmount;118             off += nextTransferAmount;119             in += nextTransferAmount;120             if (in >= buffer.length) {121                 in = 0;122             }123         }124     }125 126     // 检查管道状态127     private void checkStateForReceive() throws IOException {128         if (!connected) {129             throw new IOException("Pipe not connected");130         } else if (closedByWriter || closedByReader) {131             throw new IOException("Pipe closed");132         } else if (readSide != null && !readSide.isAlive()) {133             throw new IOException("Read end dead");134         }135     }136 137     // 等待。138     // 若“写入管道”的数据正好全部被读取完(例如，管道缓冲满)，则执行awaitSpace()操作；139     // 它的目的是让“读取管道的线程”管道产生读取数据请求，从而才能继续的向“管道”中写入数据。140     private void awaitSpace() throws IOException {141         142         // 如果“管道中被读取的数据，等于写入管道的数据”时，143         // 则每隔1000ms检查“管道状态”，并唤醒管道操作：若有“读取管道数据线程被阻塞”，则唤醒该线程。144         while (in == out) {145             checkStateForReceive();146 147             /* full: kick any waiting readers */148             notifyAll();149             try {150                 wait(1000);151             } catch (InterruptedException ex) {152                 throw new java.io.InterruptedIOException();153             }154         }155     }156 157     // 当PipedOutputStream被关闭时，被调用158     synchronized void receivedLast() {159         closedByWriter = true;160         notifyAll();161     }162 163     // 从管道(的缓冲)中读取一个字节，并将其转换成int类型164     public synchronized int read()  throws IOException {165         if (!connected) {166             throw new IOException("Pipe not connected");167         } else if (closedByReader) {168             throw new IOException("Pipe closed");169         } else if (writeSide != null && !writeSide.isAlive()170                    && !closedByWriter && (in < 0)) {171             throw new IOException("Write end dead");172         }173 174         readSide = Thread.currentThread();175         int trials = 2;176         while (in < 0) {177             if (closedByWriter) {178                 /* closed by writer, return EOF */179                 return -1;180             }181             if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) {182                 throw new IOException("Pipe broken");183             }184             /* might be a writer waiting */185             notifyAll();186             try {187                 wait(1000);188             } catch (InterruptedException ex) {189                 throw new java.io.InterruptedIOException();190             }191         }192         int ret = buffer[out++] & 0xFF;193         if (out >= buffer.length) {194             out = 0;195         }196         if (in == out) {197             /* now empty */198             in = -1;199         }200 201         return ret;202     }203 204     // 从管道(的缓冲)中读取数据，并将其存入到数组b中205     public synchronized int read(byte b[], int off, int len)  throws IOException {206         if (b == null) {207             throw new NullPointerException();208         } else if (off < 0 || len < 0 || len > b.length - off) {209             throw new IndexOutOfBoundsException();210         } else if (len == 0) {211             return 0;212         }213 214         /* possibly wait on the first character */215         int c = read();216         if (c < 0) {217             return -1;218         }219         b[off] = (byte) c;220         int rlen = 1;221         while ((in >= 0) && (len > 1)) {222 223             int available;224 225             if (in > out) {226                 available = Math.min((buffer.length - out), (in - out));227             } else {228                 available = buffer.length - out;229             }230 231             // A byte is read beforehand outside the loop232             if (available > (len - 1)) {233                 available = len - 1;234             }235             System.arraycopy(buffer, out, b, off + rlen, available);236             out += available;237             rlen += available;238             len -= available;239 240             if (out >= buffer.length) {241                 out = 0;242             }243             if (in == out) {244                 /* now empty */245                 in = -1;246             }247         }248         return rlen;249     }250 251     // 返回不受阻塞地从此输入流中读取的字节数。252     public synchronized int available() throws IOException {253         if(in < 0)254             return 0;255         else if(in == out)256             return buffer.length;257         else if (in > out)258             return in - out;259         else260             return in + buffer.length - out;261     }262 263     // 关闭管道输入流264     public void close()  throws IOException {265         closedByReader = true;266         synchronized (this) {267             in = -1;268         }269     }270 }

 1 import java.io.IOException;    2     3 import java.io.PipedInputStream;    4     5 @SuppressWarnings("all")    6 /**   7  * 接收者线程   8  */    9 public class Receiver extends Thread {   10        11     // 管道输入流对象。12     // 它和“管道输出流(PipedOutputStream)”对象绑定，13     // 从而可以接收“管道输出流”的数据，再让用户读取。14     private PipedInputStream in = new PipedInputStream();   15    16     // 获得“管道输入流”对象17     public PipedInputStream getInputStream(){   18         return in;   19     }   20        21     @Override22     public void run(){   23         readMessageOnce() ;24         //readMessageContinued() ;25     }26 27     // 从“管道输入流”中读取1次数据28     public void readMessageOnce(){29         // 虽然buf的大小是2048个字节，但最多只会从“管道输入流”中读取1024个字节。30         // 因为，“管道输入流”的缓冲区大小默认只有1024个字节。31         byte[] buf = new byte[2048];32         try {33             int len = in.read(buf);34             System.out.println(new String(buf,0,len));35             in.close();36         } catch (IOException e) {37             e.printStackTrace();38         }39     }40     // 从“管道输入流”读取>1024个字节时，就停止读取41     public void readMessageContinued() {42         int total=0;43         while(true) {44             byte[] buf = new byte[1024];45             try {46                 int len = in.read(buf);47                 total += len;48                 System.out.println(new String(buf,0,len));49                 // 若读取的字节总数>1024，则退出循环。50                 if (total > 1024)51                     break;52             } catch (IOException e) {53                 e.printStackTrace();54             }55         }56 57         try {58             in.close();59         } catch (IOException e) {60             e.printStackTrace();61         }62     }63 }

 1 import java.io.IOException;    2     3 import java.io.PipedOutputStream;    4 @SuppressWarnings("all") 5 /**   6  * 发送者线程   7  */    8 public class Sender extends Thread {    9        10     // 管道输出流对象。11     // 它和“管道输入流(PipedInputStream)”对象绑定，12     // 从而可以将数据发送给“管道输入流”的数据，然后用户可以从“管道输入流”读取数据。13     private PipedOutputStream out = new PipedOutputStream();14 15     // 获得“管道输出流”对象16     public PipedOutputStream getOutputStream(){17         return out;18     }   19 20     @Override21     public void run(){   22         writeShortMessage();23         //writeLongMessage();24     }   25 26     // 向“管道输出流”中写入一则较简短的消息："this is a short message" 27     private void writeShortMessage() {28         String strInfo = "this is a short message" ;29         try {30             out.write(strInfo.getBytes());31             out.close();   32         } catch (IOException e) {   33             e.printStackTrace();   34         }   35     }36     // 向“管道输出流”中写入一则较长的消息37     private void writeLongMessage() {38         StringBuilder sb = new StringBuilder();39         // 通过for循环写入1020个字节40         for (int i=0; i<102; i++)41             sb.append("0123456789");42         // 再写入26个字节。43         sb.append("abcdefghijklmnopqrstuvwxyz");44         // str的总长度是1020+26=1046个字节45         String str = sb.toString();46         try {47             // 将1046个字节写入到“管道输出流”中48             out.write(str.getBytes());49             out.close();50         } catch (IOException e) {51             e.printStackTrace();52         }53     }54 }

 1 import java.io.PipedInputStream; 2 import java.io.PipedOutputStream; 3 import java.io.IOException; 4  5 @SuppressWarnings("all")    6 /**   7  * 管道输入流和管道输出流的交互程序 8  */    9 public class PipedStreamTest {   10    11     public static void main(String[] args) {   12         Sender t1 = new Sender();   13            14         Receiver t2 = new Receiver();   15            16         PipedOutputStream out = t1.getOutputStream();   17  18         PipedInputStream in = t2.getInputStream();   19 20         try {   21             //管道连接。下面2句话的本质是一样。22             //out.connect(in);   23             in.connect(out);   24                25             /**  26              * Thread类的START方法：  27              * 使该线程开始执行；Java 虚拟机调用该线程的 run 方法。   28              * 结果是两个线程并发地运行；当前线程（从调用返回给 start 方法）和另一个线程（执行其 run 方法）。   29              * 多次启动一个线程是非法的。特别是当线程已经结束执行后，不能再重新启动。   30              */31             t1.start();32             t2.start();33         } catch (IOException e) {34             e.printStackTrace();35         }36     }37 }