How to fix NullPointerException: uri

Question

I am building an Android application and starting to learn to save the images. What I am trying to do is saving bitmap to a folder in DCIM, so I am calling the function save Image and passing the bitmap.However when I try to save it, the app crash with the error.

Calling the function

saveImage(bitmap,"Face");

The saveImage function

 private void saveImage(Bitmap bitmap, @NonNull String name) throws IOException {
        boolean saved;
        OutputStream fos;

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            ContentResolver resolver = getApplicationContext().getContentResolver();
            ContentValues contentValues = new ContentValues();
            contentValues.put(MediaStore.MediaColumns.DISPLAY_NAME, name);
            contentValues.put(MediaStore.MediaColumns.MIME_TYPE, "image/png");
            contentValues.put(MediaStore.MediaColumns.RELATIVE_PATH, "DCIM/" + IMAGES_FOLDER_NAME);
            Uri imageUri = resolver.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues);
            fos = resolver.openOutputStream(imageUri);
        } else {
            String imagesDir = Environment.getExternalStoragePublicDirectory(
                    Environment.DIRECTORY_DCIM).toString() + File.separator + IMAGES_FOLDER_NAME;

            File file = new File(imagesDir);

            if (!file.exists()) {
                file.mkdir();
            }

            File image = new File(imagesDir, name + ".png");
            fos = new FileOutputStream(image);

        }

        saved = bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);
        fos.flush();
        fos.close();
        Log.e("Save Image", "successfully");
    }

Error message

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.fypredo, PID: 6996
    java.lang.NullPointerException: uri
        at com.android.internal.util.Preconditions.checkNotNull(Preconditions.java:133)
        at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:1488)
        at android.content.ContentResolver.openOutputStream(ContentResolver.java:1238)
        at android.content.ContentResolver.openOutputStream(ContentResolver.java:1214)