Process需要注意

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    Process创建的子进程没有自己的终端或控制台

 import java.io.*;import java.util.*;public class PrivateClass{   static final String COMMAND = "java PrivateClass slave"; public static void main(String[] args) throws Exception {       if(args.length == 1 && args[0].equals("slave"))  {   for(int i = 20; i > 0; i--)    {    System.out.println( i +    " bottles of beer on the wall" );    System.out.println(i + " bottles of beer");    System.out.println(    "You take on down, pass it around,");    System.out.println( (i-1) +    " bottles of beer on the wall");    System.out.println();    }  }  else  {     //Process process =new ProcessBuilder("java PrivateClass", "slave").start();     Process process = Runtime.getRuntime().exec(COMMAND);     drainInBackground(process.getInputStream());//这样就可以看到调用程序运行的结果     int exitValue = process.waitFor();     System.out.println("exit value = " + exitValue);  }   }  static void drainInBackground(final InputStream is) {  new Thread()  {   public void run()   {    /*     用下面这个是一样一样的     Scanner s=new Scanner(is);    while(s.hasNextLine())     System.out.println(s.nextLine());    System.out.println("结束");    */

    try    {    BufferedReader br=new BufferedReader(new InputStreamReader(is));    String temp;    while((temp=br.readLine())!=null)     System.out.println(temp);    }    catch(IOException e)    {         }   }  }.start(); }}

经过实际测试，发现   System.out.println("exit value = " + exitValue);这一句不是最后才打印出来的，它可能在子线程中间就输出于是我改了一下子程序，算是小技巧吧

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import java.io.*;import java.util.*;public class PrivateClass{   static final String COMMAND = "java PrivateClass slave"; public static void main(String[] args) throws Exception {  if(args.length == 1 && args[0].equals("slave"))  {   for(int i = 80; i > 0; i--)    {    System.out.println( i +    " bottles of beer on the wall" );    System.out.println(i + " bottles of beer");    System.out.println(    "You take on down, pass it around,");    System.out.println( (i-1) +    " bottles of beer on the wall");    System.out.println();    }  }  else  {     Process process = Runtime.getRuntime().exec(COMMAND);     ThreadInBack tib=new ThreadInBack(process.getInputStream());     tib.start();     tib.join();     int exitValue = process.waitFor();     System.out.println("exit value = " + exitValue);  }   } }

class ThreadInBack extends Thread{ InputStream is;    public ThreadInBack(InputStream is) {  this.is=is; } public void run() {      Scanner s=new Scanner(is);  while(s.hasNextLine())   System.out.println(s.nextLine());  System.out.println("结束");     } }