ErgoReducedSendTransaction.java

    private ReducedTransaction getReducedSendTx(boolean isMainNet, long amountToSend, Address sender, Address recipient) {
        NetworkType networkType = isMainNet ? NetworkType.MAINNET : NetworkType.TESTNET;
        return RestApiErgoClient.create(
                getDefaultNodeUrl(isMainNet),
                networkType,
                "",
                RestApiErgoClient.getDefaultExplorerUrl(networkType)
        ).execute(ctx -> {
            ErgoTreeContract contract = new ErgoTreeContract(recipient.getErgoAddress().script());
            UnsignedTransaction unsignedTransaction = BoxOperations.putToContractTxUnsigned(ctx,
                    Collections.singletonList(sender),
                    contract, amountToSend, Collections.emptyList());
            return ctx.newProverBuilder().build().reduce(unsignedTransaction, 0);
        });
    }

    public static final String NODE_MAINNET = "http://213.239.193.208:9053/";
    public static final String NODE_TESTNET = "http://213.239.193.208:9052/";

    private static String getDefaultNodeUrl(boolean mainNet) {
        return mainNet ? NODE_MAINNET : NODE_TESTNET;
    }