check permission and request permission

file.java

//Add this line in import section
import static android.Manifest.permission.CAMERA;

private void requestPermission() {
    ActivityCompat.requestPermissions(this, new String[]{CAMERA}, PERMISSION_REQUEST_CODE);
}

private boolean checkPermission() {
    return ContextCompat.checkSelfPermission(getApplicationContext(), CAMERA) == PackageManager.PERMISSION_GRANTED;
}