android 判断一个包是否在系统存在

private boolean hasBrowser(){
  PackageManager pm = getPackageManager();
   List<PackageInfo> lsPackageInfo = pm.getInstalledPackages(0);
   boolean flag = false;
   String weiboPackageName = "";
   for (PackageInfo pi : lsPackageInfo){
    if (pi.packageName.contains("com.android.browser")) {
     flag = true;
     break;
    }
   }
   return flag;
 }