java多线程编程之管道通信详解

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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

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