gistfile1.txt

if (!Environment.isExternalStorageManager()) {
    Intent intent = new Intent(Settings.ACTION_MANAGE_ALL_FILES_ACCESS_PERMISSION);
    intent.setData(Uri.parse("package:" + getPackageName()));
    startActivity(intent); // directs user to settings screen
}

gistfile2.txt

ContentValues values = new ContentValues();
values.put(MediaStore.Files.FileColumns.DISPLAY_NAME, "Report.pdf");
values.put(MediaStore.Files.FileColumns.MIME_TYPE, "application/pdf");
values.put(MediaStore.Files.FileColumns.RELATIVE_PATH, Environment.DIRECTORY_DOCUMENTS); 
// RELATIVE_PATH "Documents" directs it to /storage/emulated/0/Documents
Uri uri = getContentResolver().insert(MediaStore.Files.getContentUri("external"), values);
if (uri != null) {
    try (OutputStream out = getContentResolver().openOutputStream(uri)) {
        // Write your file data to the stream
    }
}