线程间数据传输

线程之间只是简单的等待和唤醒并不能满足我们的需求，如果能让多个线程之间实现数据传输的话岂不是更好。

java中提供了各种各样的输入／输出流stream，是我们能够很方便的对数据进行操作，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取数据。通过使用管道，实现不同线程间的通信，而无需借助于类型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（用于传输字节流） 2. PipedReader和PipedWriter（用于传输字符流）

示例代码：

// class WriteData public class WriteData { public void writeMethod(PipedOutputStream out) { try{ System.out.println("write : "); for(int i = 0; i < 100; ++ i) { String outData = "" + (i + 1); out.write(outData.getBytes()); System.out.print(outData); } System.out.println(); out.close(); } catch(IOException e) { e.printStackTrace(); } } } // class ReadData 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(); } } } // class ThreadWrite public class ThreadWrite extends Thread { private WriteData write; private PipedOutputStream out; public ThreadWrite(WriteData write, PipedOutputStream out) { this.write = write; this.out = out; } @Override public void run() { write.writeMethod(out); } } // class ThreadRead public class ThreadRead extends Thread { private ReadData read; private PipedInputStream input; public ThreadRead(ReadData read, PipedInputStream input) { this.read = read; this.input = input; } @Override public void run() { read.readMethod(input); } } // class Main public class Main { public static void main(String[] args) { threadStream(); } private static void threadStream() { try{ WriteData wirteData = new WriteData(); ReadData readData = new ReadData(); PipedInputStream inputStream = new PipedInputStream(); PipedOutputStream outputStream = new PipedOutputStream(); //inputStream.connect(outputStream); outputStream.connect(inputStream); ThreadRead threadRead = new ThreadRead(readData, inputStream); threadRead.start(); Thread.sleep(2000); ThreadWrite threadWrite = new ThreadWrite(wirteData, outputStream); threadWrite.start(); } catch(IOException e) { e.printStackTrace(); } catch(InterruptedException e) { e.printStackTrace(); } } }

使用代码inputStream.connect(outputStream)或outputStream.connect(inputStream)使两个stream之间产生通信链接，这样才可以将数据进行输出和输入。

输出结果：

read : write : 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100

从程序的打印结果来看，两个线程通过管道流成功实现了数据的传输（字符流同上）。