通过Java中的管道流丢失数据

Question

我正在为我的 Java 并行和并发编程课程做一项实验室工作。目前，我正在尝试使用管道流在线程之间进行通信。我正在使用 java.io 库中的 PipedWriter 和 PipedReader。由于某种原因，我发送的一些消息在线程之间通信时丢失了。

更具体地说，这是一个屏幕截图。

http://screencloud.net/v/bicK

如你所见，我也得到了一些奇异的符号，这通常不是好兆头:)

这是我的线程类

package lab2_string;

import java.io.*;

public class StringRunnable implements Runnable{

    int threadNr;
    PipedReader in;
    PipedWriter out;
    String msg = "";
    @Override
    public void run() {
        readStream();
        System.out.println("Thread nr: " + threadNr);
        System.out.println("Message: " + msg);
        writeToStream();
    }

    public StringRunnable(PipedReader rs, PipedWriter ws, int threadNr){
        try{
            out = ws;
            in = rs;
            this.threadNr = threadNr;
        }catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

    public void writeToStream(){
        try{
            out.write(msg);
            out.flush();
            out.close();
        }catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }


    public void readStream(){
        try{
            while(in.read()!=-1){
                char c = (char) in.read();
                msg = msg + c;
            }in.close();
        }catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

}

还有我的主程序类

package lab2_string;

import java.io.*;

public class Lab2 {

    public static void main(String[] args) {
        try{

            PipedWriter pwOut1 = new PipedWriter();
            PipedReader pwIn1 = new PipedReader(pwOut1);
            PipedWriter pwOut2 = new PipedWriter();
            PipedReader pwIn2 = new PipedReader(pwOut2);
            PipedWriter pwOut3 = new PipedWriter();

            Thread t1;
            Thread t2;

            t1 = new Thread(new StringRunnable(pwIn1,pwOut2,1));
            t2 = new Thread(new StringRunnable(pwIn2,pwOut3,2));
            t1.start();
            t2.start();

            pwOut1.write("Andrew");
            pwOut1.flush();
            pwOut1.close();


        }catch (Exception e) {
            System.out.println("Error:" + e);
        }

    }

}

请帮助我了解是什么原因造成的，我该如何解决它！

Answer 1

你的 in.read() 调用被执行了两次，并且只存储在变量中一次。

public void readStream(){
        try{
            while(in.read()!=-1){
                char c = (char) in.read();
                msg = msg + c;
            }in.close();
        }catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

注意 in.read() 在 while 循环中被调用（使得 in.read() 返回的字符不存储在 c 变量中并跳过字符），

一个更好的例子可能类似于...

try{
    char c;
    while((c = (char)in.read()) != -1) {
        msg += c;
    }
    in.close();
} catch(Exception e){
    System.out.println("Error: " + e);
}

精明？