多线程编程之线程间的通信——管道通信

上一章节讲了wait/notify通信，这一节我们来探讨使用管道进行通信。
java中提供了IO流使我们很方便的对数据进行操作，pipeStream是一种特殊的流，用于不同线程间直接传送数据。一个线程将数据发送到输出管道，另一个线程从输入管道读取数据。通过管道实现通信不需要借助临时文件这类东西。
java中提供了四个类使得线程间可以通信：
①字节流：PipeInputStream，PipedOutputStream
②字符流：PipedReader，PipedWriter

下面我们看看字节流的实现方法：

package pipeInputOutput;//输出流import java.io.IOException;import java.io.PipedOutputStream;public class WriteDate {    public void writeMethod(PipedOutputStream out) {        try {            System.out.println("write:");            for(int i=0;i<300;i++) {                String outDate=""+(i+1);                out.write(outDate.getBytes());                System.out.print(outDate);            }            System.out.println();            out.close();        }catch(IOException e) {            e.printStackTrace();        }    }}package pipeInputOutput;//输入流import java.io.IOException;import java.io.PipedInputStream;public class ReadDate {    public void ReadDate(PipedInputStream input) {        try {            System.out.println("read:");            byte[] byteArray=new byte[20];            int readLength=input.read(byteArray);            while(readLength!=-1) {                String newDate=new String(byteArray,0,readLength);                System.out.print(newDate);                readLength=input.read(byteArray);            }            System.out.println();            input.close();        }catch(IOException e){            e.printStackTrace();        }       }}package pipeInputOutput;import java.io.PipedOutputStream;//输出线程public class ThreadWrite extends Thread {    private WriteDate write;    private PipedOutputStream out;    public ThreadWrite(WriteDate write,PipedOutputStream out) {        super();        this.write=write;        this.out=out;    }    public void run() {        write.writeMethod(out);    }}package pipeInputOutput;import java.io.PipedInputStream;//输入线程public class ThreadRead extends Thread{    private ReadDate read;    private PipedInputStream in;    public ThreadRead(ReadDate read,PipedInputStream in) {        super();        this.read=read;        this.in=in;    }    public void run() {        read.ReadDate(in);    }}package pipeInputOutput;import java.io.IOException;import java.io.PipedInputStream;import java.io.PipedOutputStream;//测试方法public class Run {    public static void main(String[] args) {        try {            WriteDate write=new WriteDate();            ReadDate read=new ReadDate();            PipedInputStream inputStream=new PipedInputStream();            PipedOutputStream outputStream=new PipedOutputStream();            //输出流与输入流进行连接。            outputStream.connect(inputStream);            //inputStream.connect(outputStream);            ThreadRead readThread=new ThreadRead(read,inputStream);            readThread.start();//先启动输出线程            Thread.sleep(2000);            ThreadWrite writeThread=new ThreadWrite(write,outputStream);            writeThread.start();//后启动输入线程        } catch (IOException e) {            e.printStackTrace();        } catch (InterruptedException e) {            e.printStackTrace();        }    }}控制台输出：read:write:123456789101112131415161718192021...123456789101112131415161718192021...

上面测试中，先启动输入线程，然后因为没有线程被写入所以线程被阻塞，知道有数据写入。

我们接着继续看看字符流的实现方法：

package pipeInputOutput1;import java.io.IOException;import java.io.PipedWriter;//字符输出流public class WriteDate {    public void writeMethod(PipedWriter out) {        try {            System.out.println("write:");            for(int i=0;i<300;i++) {                String outDate=""+(i+1);                out.write(outDate);                System.out.print(outDate);            }            System.out.println();            out.close();        }catch(IOException e) {            e.printStackTrace();        }    }}package pipeInputOutput1;import java.io.IOException;import java.io.PipedReader;//字符输入流public class ReadDate {    public void readMethod(PipedReader in) {        try {            System.out.println("read:");            char[] byteArray=new char[20];            int readLength=in.read(byteArray);            while(readLength!=-1) {                String newDate=new String(byteArray,0,readLength);                System.out.print(newDate);                readLength=in.read(byteArray);            }            System.out.println();            in.close();        } catch (IOException e) {            e.printStackTrace();        }    }}package pipeInputOutput1;import java.io.PipedWriter;//输出流线程public class WriteThread extends Thread {    private WriteDate write;    private PipedWriter out;    public WriteThread(WriteDate write,PipedWriter out) {        super();        this.write=write;        this.out=out;    }    public void run() {        write.writeMethod(out);    }}package pipeInputOutput1;import java.io.PipedReader;//输入流线程public class ReadThread extends Thread{    private ReadDate read;    private PipedReader in;    public ReadThread(ReadDate read,PipedReader in) {        super();        this.read=read;        this.in=in;    }    public void run() {        read.readMethod(in);    }}package pipeInputOutput1;import java.io.IOException;import java.io.PipedReader;import java.io.PipedWriter;//测试方法public class run {    public static void main(String[] args) {        try {            WriteDate write=new WriteDate();            ReadDate read=new ReadDate();            PipedWriter out=new PipedWriter();            PipedReader in=new PipedReader();            //连接输出流与输入流            out.connect(in);            //in.connect(out);            ReadThread threadread=new ReadThread(read,in);            threadread.start();            Thread.sleep(2000);            WriteThread threadwrite=new WriteThread(write,out);            threadwrite.start();        } catch (IOException e) {            e.printStackTrace();        } catch (InterruptedException e) {            e.printStackTrace();        }    }}

字符流额字节流大同小异，上面的例子中字符流不需要创建字节数组而已。