if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
        == PackageManager.PERMISSION_GRANTED) {
    // Do code here
} else {
    // Request permission here
}

• Use ActivityCompat.requestPermissions() to request permissions

if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA) {
    Snackbar.make(mAnchorLayout, "Camera permission is needed to attach pictures",
            Snackbar.LENGTH_INDEFINITE)
            .setAction(R.string.ok, new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    ActivityCompat.requestPermissions(MainActivity.this,
                            new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA);
                }
            })
            .show();
} else {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA},
            REQUEST_CAMERA);
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
        @NonNull int[] grantResults) {

    if (requestCode == REQUEST_CAMERA) {
        if (grantResults.length == 1 && grantResults[0] ==               
            PackageManager.PERMISSION_GRANTED) {

            Snackbar.make(mAnchorLayout, "You can now take photos",
                    Snackbar.LENGTH_SHORT).show();
        } else {

            Snackbar.make(mAnchorLayout, "Permission not granted",
                    Snackbar.LENGTH_SHORT).show();
        }
    } 
}