class WalletManager {

    public int getPositionByAddress(String address) {
        return Flowable
                .range(0, mWalletList.size())
                .filter(new Predicate<Integer>() {
                    @Override
                    public boolean test(Integer integer) throws Exception {
                        return mWalletList.get(integer).getPrefixAddress().equalsIgnoreCase(address);
                    }
                })
                .firstElement()
                .defaultIfEmpty(-1)
                .onErrorReturnItem(-1)
                .blockingGet();
    }

    private  WalletManager();

}