We have not released a new Java SDK version to support High Volume SMS yet. Right now, you can use the current RingCentral Java SDK version this way.

public class Message {

    public String[] to;

    public String text = "";

}

public class A2PBody {

    public String from = "";

    public String text = "";

    public Message[] messages;

}

public class Filters {

    public String view = "";

    public String dateFrom = "";

    public String dateTo = "";

}

// if you want to broadcast a single message to multiple recipients

public void broadcast_a2p_sms() throws RestException, IOException{

    A2PBody body = new A2PBody();

    body.from = "Your-HighVolume-SMS-Number";

    body.text = "Hello High Volume SMS from Java";

    String[] recipients = new String[] {"+1650xxxxxxx", "+1408xxxxxxx"};

    Message[] messages = new Message[2];

    for (int i=0; i<messages.length; i++) {

        Message m = new Message();

        m.to = new String[] {recipients[i]};

        messages[i] = m;

    }

    body.messages = messages;

    ResponseBody resp = restClient.post("/restapi/v1.0/account/~/a2p-sms/batch", body);

    System.out.println(resp.string());

}

// if you want to send custom message to each recipient

public void send_a2p_sms() throws RestException, IOException{

    A2PBody body = new A2PBody();

    body.from = "Your-HighVolume-SMS-Number";

    body.text = "";

    String[] recipients = new String[] {"+1650xxxxxxx", "+1408xxxxxxx"};

    String[] names = new String[] {"John Smith", "Matthew Frank"};

    Message[] messages = new Message[2];

    for (int i=0; i<messages.length; i++) {

        Message m = new Message();

        m.text = "Hello " + names[i];

        m.to = new String[] {numbers[i]};

        messages[i] = m;

    }

    body.messages = message

    ResponseBody resp = restClient.post("/restapi/v1.0/account/~/a2p-sms/batch", body);

    System.out.println(resp.string());

}

// read the HV SMS message store

public void get_a2p_sms() throws RestException, IOException {

    var params = new Filters();

    params.view = "Detailed";

    params.dateFrom = "2021-01-01T00:00:00.000Z";

    params.dateTo = "2021-01-21T00:00:00.000Z";



    ResponseBody resp = restClient.get("/restapi/v1.0/account/~/a2p-sms/messages", params);

    System.out.println(resp.string());

}

Check out the Dev Guide for more details about reading the HV SMS message store.