void installApp(String fileName) {
        Intent intent = new Intent(Intent.ACTION_VIEW)
            .setDataAndType(Uri.parse("file://" + fileName), "application/vnd.android.package-archive");
        startActivity(intent);
    }

    void removeApp(String packageName) {
        Intent intent = new Intent(Intent.ACTION_DELETE)
            .setData(Uri.parse("package:" + packageName));
        startActivity(intent);
    }

    boolean getApplicationInstalled(String pkgName) {
        ApplicationInfo appInfo = null;
   
        final PackageManager pm = getPackageManager();
        try {
            appInfo = pm.getApplicationInfo(pkgName, PackageManager.GET_META_DATA);
        } catch (NameNotFoundException e) {
            e.printStackTrace();
        }  
   
        if(appInfo != null) return true;
        else return false;
    }