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);}