Java Runtime.exec运行交互式外壳

Question

我尝试在Java中执行Windows命令cmd，用命令将其馈送，然后在控制台上打印输出或错误。但是，在打印横幅消息后，我的尝试悬而未决。这是代码。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
public class Application {
    public static void main(String[] args) throws IOException, InterruptedException {
        Process exec = Runtime.getRuntime().exec("cmd");
        InputStream procOut = exec.getInputStream();
        InputStream procErrOut = exec.getErrorStream();
        OutputStream procIn = exec.getOutputStream();
        new StreamConsumer(procOut).run();
        new StreamConsumer(procErrOut).run();
        ByteArrayOutputStream byos = new ByteArrayOutputStream();
        byos.write("ping 1.1.1.1".getBytes());
        byos.writeTo(procIn);
        byos.flush();
        procIn.flush();
        int ret = exec.waitFor();
        System.out.printf("Process exited with value %d", ret);
    }
    public static class StreamConsumer implements Runnable {
        private InputStream input;
        public StreamConsumer(InputStream input) {
            this.input = input;
        }
        @Override
        public void run() {
            BufferedReader reader = new BufferedReader(new InputStreamReader(input));
            String line;
            try {
                while ((line = reader.readLine()) != null) {
                    System.out.println(line);
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                try {
                    reader.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}

这是输出

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.
** program hangs **

为什么程序悬挂而没有执行（或打印）？我了解必须消耗这些流以避免悬挂（我在单独的线程中进行），但仍然悬挂。我是否误解了输出流是如何将输出流传输到交互式外壳的？

Answer 1

您必须启动线程以消耗输出：

        new Thread(new StreamConsumer(procOut)).start();
        new Thread(new StreamConsumer(procErrOut)).start();