在Java语言中提供了各种各样的输入/输出流Stream，使我们能够很方便地对数据进行操作，其中管道流（pipeStream）是一种特殊的流，用于在不同线程间直接传送数据。一个线程发送数据到输出管道，另一个线程从输入管道中读数据。通过使用管道，实现不同线程间的通信，而无须借助于类似临时文件之类的东西。
在Java的JDK中提供了4个类来使线程间可以进行通信：

1）PipedInputStream和PipedOutputStream
2）PipedReader和PipedWriter
创建测试用的项目pipeInputOutput。
类WriteData.java代码如下：

package service;
import java.io.IOException;
import java.io.PipedOutputStream;
public class  {
  public void writeMethod(PipedOutputStream out) {
    try {
      System.out.println("write :");
      for (int i = 0; i < 300; i++) {
        String outData = "" + (i + 1);
        out.write(outData.getBytes());
        System.out.print(outData);
      }
      System.out.println();
      out.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

类ReadData.java代码如下：

package service;
import java.io.IOException;
import java.io.PipedInputStream;
public class ReadData {
  public void readMethod(PipedInputStream input) {
    try {
      System.out.println("read  :");
      byte[] byteArray = new byte[20];
      int readLength = input.read(byteArray);
      while (readLength != -1) {
        String newData = new String(byteArray, 0, readLength);
        System.out.print(newData);
        readLength = input.read(byteArray);
      }
      System.out.println();
      input.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

两个自定义线程代码如图3-37所示：

类Run.java代码如下：

package test;
import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import service.ReadData;
import service.WriteData;
import extthread.ThreadRead;
import extthread.ThreadWrite;
public class Run {
  public static void main(String[] args) {
    try {
      WriteData writeData = new WriteData();
      ReadData readData = new ReadData();
      PipedInputStream inputStream = new PipedInputStream();
      PipedOutputStream outputStream = new PipedOutputStream();
      
      outputStream.connect(inputStream);
      ThreadRead threadRead = new ThreadRead(readData, inputStream);
      threadRead.start();
      Thread.sleep(2000);
      ThreadWrite threadWrite = new ThreadWrite(writeData, outputStream);
      threadWrite.start();
    } catch (IOException e) {
      e.printStackTrace();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}

使用代码inputStream.connect（outputStream）或outputStream.connect（inputStream）的作用使两大专栏 Java技术之线程通信个Stream之间产生通信链接，这样才可以将数据进行输出与输入。
程序运行结果如图3-38所示：

2. 通过管道进行线程间通信：字符流

当然，在管道中还可以传递字符流。
创建测试用的项目pipeReaderWriter。

类WriteData.java代码如下：

package service;
import java.io.IOException;
import java.io.PipedWriter;
public class  {
  public void writeMethod(PipedWriter out) {
    try {
      System.out.println("write :");
      for (int i = 0; i < 300; i++) {
        String outData = "" + (i + 1);
        out.write(outData);
        System.out.print(outData);
      }
      System.out.println();
      out.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

类ReadData.java代码如下：

package service;
import java.io.IOException;
import java.io.PipedReader;
public class ReadData {
  public void readMethod(PipedReader input) {
    try {
      System.out.println("read  :");
      char[] byteArray = new char[20];
      int readLength = input.read(byteArray);
      while (readLength != -1) {
        String newData = new String(byteArray, 0, readLength);
        System.out.print(newData);
        readLength = input.read(byteArray);
      }
      System.out.println();
      input.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

两个自定义线程代码如图3-39所示：

类Run.java代码如下：

package test;
import java.io.IOException;
import java.io.PipedReader;
import java.io.PipedWriter;
import service.ReadData;
import service.WriteData;
import extthread.ThreadRead;
import extthread.ThreadWrite;
public class Run {
  public static void main(String[] args) {
    try {
      WriteData writeData = new WriteData();
      ReadData readData = new ReadData();
      PipedReader inputStream = new PipedReader();
      PipedWriter outputStream = new PipedWriter();
      
      outputStream.connect(inputStream);
      ThreadRead threadRead = new ThreadRead(readData, inputStream);
      threadRead.start();
      Thread.sleep(2000);
      ThreadWrite threadWrite = new ThreadWrite(writeData, outputStream);
      threadWrite.start();
    } catch (IOException e) {
      e.printStackTrace();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}

程序运行结果如图3-40所示：

打印的结果和前一个示例基本一样，此实验是在两个线程中通过管道流进行字符数据的传输。

Java技术之线程通信

2. 通过管道进行线程间通信：字符流

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