Instead of using preferences you can use Sqlite database. But if you insist on using SharedPreferences then I don't think you have much choice as you can only store boolean, float, int, long, String or StringSet. The only possible way I see is that you concatenate all of the values with your own separator like
1123.4456:1234.223|1123.4456:1234.1233|1123.4456:1234.223|1123.4456:1234.223
and then just parse when retrieving it.