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：
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| 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：
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| 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：
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| 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();
}
}
}
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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：
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| 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：
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| 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：
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| 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。