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 WriteDatapublic 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 ReadDatapublic 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 ThreadWritepublic 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 ThreadReadpublic 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 Mainpublic 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 : 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100

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）。