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）。