Going through Master Card API docs to see how to integrate it, saw that they have sample code, checked Java sample code and found this:

String data = MessageFormat.format(
"'{'\"apiOperation\":{0},"
+ "\"sourceOfFunds\":'{'\"type\":{1},\"provided\":'{'\"card\":'{'\"numbe\":{2},"
+ "\"expiry\":'{'\"month\":{3}, \"year\":{4}'}',\"securityCode\":{5}'}}}',"
+ "\"order\":'{'\"reference\":{6}'}',"
+ "\"transaction\":'{'\"amount\":{7},\"currency\":{8},\"reference\":{9},\"targetTransactionId\":{10}'}'," + "\"customer\":'{'\"ipAddress\":{11}'}}'",
apiOperation,
sourceOfFundsType,
cardNumber,
cardExpiryMonth,
cardExpiryYear,
cardSecurityCode,
orderReference,
transactionAmount,
transactionCurrency,
transactionReference,
targetTransactionId,
customerIpAddress );

FOR FUCK SAKE what happened to JSONObject (for Android) class, I'm sure it is a waaaay better solution than that mess ...
And from Oracle:
JsonObject value = Json.createObjectBuilder()
.add("firstName", "John")
.add("lastName", "Smith")
.add("age", 25)
.build();

I guess that is a cleaner understandable solution than what master card has.