JAVA多线程执行cmd命令

package com.dtt.scm;


import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.LinkedList;
public class Command extends Thread{
 private java.lang.Process p; 
 private InputStream is;
 private OutputStream os;
 private BufferedWriter bw;
 private BufferedReader br;
 private ProcessBuilder pb;
 private InputStream stdErr;
 public Command() {
 }


 //获取Process的输入，输出流
 public void setCmd(String cmd) {
  try {
   p = Runtime.getRuntime().exec(cmd);
   os = p.getOutputStream();
   is = p.getInputStream();
   stdErr = p.getErrorStream();
  } catch (IOException e) {
   System.err.println(e.getMessage());
  }
 }
 //向Process输出命令
 public void writeCmd(String cmd) {
  try {
   bw = new BufferedWriter(new OutputStreamWriter(os));
   bw.write(cmd);
   bw.newLine();
   bw.flush();
   bw.close();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 //读出Process执行的结果
 public String readCmd() {
  StringBuffer sb = new StringBuffer();
  br = new BufferedReader(new InputStreamReader(is));
  String buffer = null;
  try {
   while ((buffer = br.readLine()) != null) {
    sb.append(buffer + "\n");
   }
   System.out.println(p.waitFor());
  } catch (Exception e) {
   e.printStackTrace();
  }
  return sb.toString();
 }
 //将命令一股脑塞入list中
 public LinkedList doCmd(LinkedList lists) {
  LinkedList list = new LinkedList();
  for (String s : lists) {
   writeCmd(s);
   list.add(readCmd());
  }
  return list;
 }
 public void run(){
    Command cmd = new Command();
    cmd.setCmd("cmd");
    cmd.writeCmd("start cmd /k ping -a -t 43.248.133.79 -l 1000");
    System.out.println(cmd.readCmd());
    //LinkedList list = new LinkedList();
    //list.add("dir/b");
    //list = cmd.doCmd(list);
    //for(String s:list){
    //System.out.print(s);
 }
    public static void main(String[] args) {
        Thread thr1 = new Command();
        Thread thr2 = new Command();
        thr1.start();
        thr2.start();
    }
}