android判断某个应用是否已经安装

PackageInfo packageInfo;try {     packageInfo = this.getPackageManager().getPackageInfo("com.bitcare.assistanasdft", 0);//要判断的应用的包名称} catch (NameNotFoundException e) {     packageInfo = null;     e.printStackTrace();}if (packageInfo == null) {     System.out.println("not installed");} else {     System.out.println("is installed");}