请教 kill phone 进程为什么不能成功呢

ActivityManager activityManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
List<RunningAppProcessInfo>   procList = null;
int result=-1;
procList = activityManager.getRunningAppProcesses();
for (Iterator<RunningAppProcessInfo> iterator = procList.iterator(); iterator.hasNext();) {
  RunningAppProcessInfo procInfo = iterator.next();
  if(procInfo.processName.equals("com.android.phone")) {  
    try {
      //activityManager.restartPackage(procInfo.processName);
      activityManager.killBackgroundProcesses(procInfo.processName);
    } catch (Exception e){
    }
    break;
  }
}

try {
  java.lang.Process process = Runtime.getRuntime().exec("kill -9 " + phoneId);
  // Waits for the command to finish.
  process.waitFor();
} catch (IOException e) {
  e.printStackTrace();
} catch (InterruptedException e) {
  throw new RuntimeException(e);
}