java - PipeInputStream 和 PipeOutputStream 同步还是异步？

Question

我正在读一本 Java 书，我发现一个句子似乎不正确:

When reading, if there's no data available, the thread will be blocked until it new data will be available. Notice that this is a typical asynchronous behavior, the threads are communicating through a channel(pipe).

为什么作者称该操作为“异步”？异步难道不应该意味着线程在收到新数据之前不会被阻塞吗？

稍后编辑:

我运行此代码，从输出来看，该行为似乎是异步的。

这是输出的一部分:http://ideone.com/qijn0B

代码如下。 你觉得怎么样？

import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author dragos
 */

class Consumator extends Thread{
    DataInputStream in;

    public Consumator(DataInputStream in){
        this.in = in;
    }

    public void run(){
        int value = -1;
        for(int i=0;i<=1000;i++){
            try {
                value = in.readInt();
            } catch (IOException ex) {
                Logger.getLogger(Consumator.class.getName()).log(Level.SEVERE, null, ex);
            }
            System.out.println("Consumator received: "+ value);
        }
    }
}

class Producator extends Thread{
    DataOutputStream out;

    public Producator(DataOutputStream out){
        this.out = out;
    }

    public void run(){

        for(int i=0;i<=1000;i++){
            try {
                out.writeInt(i);
            } catch (IOException ex) {
                Logger.getLogger(Producator.class.getName()).log(Level.SEVERE, null, ex);
            }
            System.out.println("Producator wrote: "+i);
        }
    }
}

public class TestPipes {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        PipedInputStream pipeIn = new PipedInputStream();
        PipedOutputStream pipeOut = new PipedOutputStream(pipeIn);

        DataInputStream in = new DataInputStream(pipeIn);
        DataOutputStream out = new DataOutputStream(pipeOut);

        Consumator c = new Consumator(in);
        Producator p = new Producator(out);

        p.start();
        c.start();

    }

}

Answer 1

Why does the author call the operation "asynchronous"? Shouldn't asynchronous imply that the thread will NOT be blocked until it receives new data?

要么这是不正确的，要么作者正在谈论消费者线程如何阻塞但生产者线程仍然运行。至少这个措辞确实令人困惑。

无论如何，PipeInputStream 和 PipeOutputStream 流共享内部缓冲区，但在其他方面都是“同步”的。如果缓冲区已满，写入器将阻塞，如果缓冲区为空，读取器将阻塞。