// First check if device is supporting flashlight or not
hasFlash = getApplicationContext().getPackageManager()
        .hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);

if (!hasFlash) {
    // device doesn't support flash
    // Show alert message and close the application
    AlertDialog alert = new AlertDialog.Builder(MainActivity.this).create();
    alert.setTitle("Error");
    alert.setMessage("Sorry, your device doesn't support flash light!");
    alert.setButton("OK", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            // closing the application
            finish();
        }
    });
    alert.show();
    return;
}