MainActivity.java

private String createUrl() {

        UId = mUser.getKey();
        if (UId.isEmpty()) {
            Snackbar.make(findViewById(R.id.main_activity_layout),
                    "You need to save your data to the cloud first!",
                    Snackbar.LENGTH_INDEFINITE)
                    .setAction("Add", new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            startActivity(new Intent(MainActivity.this, UserDataActivity.class));
                        }
                    });
            return null;
        }

        StringBuilder qBuilder = new StringBuilder();

        for (int i = 0; i < contactShareList.size(); i++) {
            String x = contactShareList.get(i);
            qBuilder.append(x);

            if (i != contactShareList.size() - 1) {
                qBuilder.append(".");
            }
        }

        String qString = qBuilder.toString();
        String queryString = null;

        queryString = Base64.encodeToString(qString.getBytes(), Base64.DEFAULT).trim();

        Log.d(TAG, "createUrl: " + queryString);

        Uri uri = new Uri.Builder()
                .scheme("https")
                .authority(AUTHORITY)
                .appendPath("api")
                .appendPath("users")
                .appendPath(UId)
                .appendPath(queryString).build();

        contactShareList.clear();
        Log.d(TAG, "createUrl: " + uri.toString());
        return uri.toString();
    }