InputStream和StreamGobbler有什么区别？

Question

In the code below, the author uses Runtime to call a sub-process. But I don't understand why he uses StreamGobbler . What will happen if replace it by InputStream ? Please help me, thanks!

public class GoodWindowsExec   
{   
    public static void main(String args[])   
    {   

        try   
        {               
            String osName = System.getProperty("os.name" );   
            System.out.println("osName: " + osName);   
            String[] cmd = new String[3];   

            if(osName.equals("Windows XP") ||osName.equals("Windows 2000"))   
            {   
                cmd[0] = "cmd.exe" ;   
                cmd[1] = "/C" ;   
                cmd[2] = args[0];   
            }   
            else if( osName.equals( "Windows 98" ) )   
            {   
                cmd[0] = "command.com" ;   
                cmd[1] = "/C" ;   
                cmd[2] = args[0];   
            }   

            Runtime rt = Runtime.getRuntime();   
            System.out.println("Execing " + cmd[0] + " " + cmd[1]+ " " + cmd[2]);   
            Process proc = rt.exec(cmd);   
            // any error message?   
            StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), "ERROR");  //Can I replace StreamGobbler by InputStream?        
            // any output?   
            StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT");   //As above

            // kick them off   
            errorGobbler.start();   
            outputGobbler.start();   

            // any error???   
            int exitVal = proc.waitFor();   
            System.out.println("ExitValue: " + exitVal);   

        } catch (Throwable t){   
            t.printStackTrace();   
        }   
    }   
}

---

BufferedReader brNormal = new BufferedReader(new InputStreamReader(process.getInputStream()));
String s = null;
while ((s = brNormal.readLine()) != null) {
    logger.info("RawToRgbConverter.exe", s);
}
brNormal.close();
BufferedReader brError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
while ((s = brError.readLine()) != null) {
    logger.error("RawToRgbConverter.exe", s);
}
brError.close();

Answer 1

Even as I don't know the StreamGobbler class, this is obviously a threaded implementation to copy the output and error streams to a given target. Thus, no you cannot simply replace it, as the multi-threading is indeed necessary. A simple input stream would just sit there, but not actually do anything.

Note however, that this complete solution is outdated since Java 1.5 which introduced the ProcessBuilder and the automatic redirects. See the javadoc at https://docs.oracle.com/javase/8/docs/api/