DejavooTransactionRequest request = new DejavooTransactionRequest();

request.setPaymentType(paymentType);
request.setTransactionType(DejavooTransactionType.Void);
request.setAmount(amount);
request.setReferenceId(refId);
request.setReceiptType(DejavooTransactionRequest.ReceiptType.Both);
request.setPrintReceipt(printReceipt);
request.setSignature(signature);
request.setSignatureCapable(signatureCapable);

terminal.sendTransactionRequest(request, new IRequestCallback<DejavooTransactionResponse>() {
    @Override
    public void onResponse(DejavooTransactionResponse response) { }

    @Override
    public void onError(DejavooThrowable e) { }
});