上一章節講了wait/notify通訊，這一節我們來探討使用管道進行通訊。
java中提供了IO流使我們很方便的對資料進行操作，pipeStream是一種特殊的流，用於不同執行緒間直接傳送資料。一個執行緒將資料傳送到輸出管道，另一個執行緒從輸入管道讀取資料。通過管道實現通訊不需要藉助臨時檔案這類東西。
java中提供了四個類使得執行緒間可以通訊：
①位元組流：PipeInputStream，PipedOutputStream
②字元流：PipedReader，PipedWriter

下面我們看看位元組流的實現方法：

package pipeInputOutput;
//輸出流
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;
//輸入流
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;
//輸出執行緒
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;
//輸入執行緒
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;
//測試方法
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();
            //輸出流與輸入流進行連線。
            outputStream.connect(inputStream);
            //inputStream.connect(outputStream);
            ThreadRead readThread=new ThreadRead(read,inputStream);
            readThread.start();//先啟動輸出執行緒
            Thread.sleep(2000);
            ThreadWrite writeThread=new ThreadWrite(write,outputStream);
            writeThread.start();//後啟動輸入執行緒
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

控制檯輸出：
read:
write:
123456789101112131415161718192021...
123456789101112131415161718192021...

上面測試中，先啟動輸入執行緒，然後因為沒有執行緒被寫入所以執行緒被阻塞，知道有資料寫入。

我們接著繼續看看字元流的實現方法：

package pipeInputOutput1;
import java.io.IOException;
import java.io.PipedWriter;
//字元輸出流
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;
//字元輸入流
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;
//輸出流執行緒
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;
//輸入流執行緒
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;
//測試方法
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();
            //連線輸出流與輸入流
            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();
        }
    }
}

字元流額位元組流大同小異，上面的例子中字元流不需要建立位元組陣列而已。