Alpha numeric sequence generator

How can I generate Alphanumeric ID efficiently like <br>
Rxt-AA0001 <br>
Rxt-AA0002 <br>
Rxt-AA0003 <br>
.. <br>
.. <br>
Rxt-AA9999 <br>
Rxt-AB0001 <br>
Rxt-AB0002 <br>

With this

public class UserIdGenerator extends SequenceStyleGenerator {
 
    public static final String VALUE_PREFIX_PARAMETER = "valuePrefix";
    public static final String VALUE_PREFIX_DEFAULT = "";
    private String valuePrefix;
 
    public static final String NUMBER_FORMAT_PARAMETER = "numberFormat";
    public static final String NUMBER_FORMAT_DEFAULT = "%d";
    private String numberFormat;
 
    @Override
    public Serializable generate(SharedSessionContractImplementor session,
            Object object) throws HibernateException {
        return valuePrefix + String.format(numberFormat, super.generate(session, object));
    }
 
    @Override
    public void configure(Type type, Properties params,
            ServiceRegistry serviceRegistry) throws MappingException {
        super.configure(LongType.INSTANCE, params, serviceRegistry);
        valuePrefix = ConfigurationHelper.getString(VALUE_PREFIX_PARAMETER,
                params, VALUE_PREFIX_DEFAULT);
        numberFormat = ConfigurationHelper.getString(NUMBER_FORMAT_PARAMETER,
                params, NUMBER_FORMAT_DEFAULT);
    }
 
}

here is my user id in model

    @Id
    @GeneratedValue(generator = "user_seq_generator", strategy = GenerationType.SEQUENCE)
    @GenericGenerator(name = "user_seq_generator", strategy = "user.util.UserIdGenerator", parameters = {
            @Parameter(name = UserIdGenerator.INCREMENT_PARAM, value = "1"),
            @Parameter(name = UserIdGenerator.VALUE_PREFIX_PARAMETER, value = "RxT-AA"),
            @Parameter(name = UserIdGenerator.NUMBER_FORMAT_PARAMETER, value = "%04d") })
    @Column(name = "user_id")
    private String Id;

I am able to generate Alpha numeric id but I am not sure how can I increment characters

Generally when creating IDs it is best practice to not increment them. This makes them insecure. This video contains a good explanation: https://www.youtube.com/watch?v=gocwRvLhDf8

Java has a build in UUID class for generating ids.
This is the javadoc for it: https://docs.oracle.com/javase/7/docs/api/java/util/UUID.html

It can be done quite simply - see the class below.

However depends on the purpose it might be more beneficial to use the UUID, as suggested by @Someone

import java.util.Arrays;
public class AlphaNumber {
public static char[] ALPHA_NUMBER_CHARS = "0123ABC".toCharArray(); // add here your characters
private int[] number = new int[32]; // here you control the maximum size of the number
private int size = 0; // here we control the actual size of the number
public AlphaNumber() {
Arrays.fill(number,0);
}
public String inc() {
for(int i=0;i<=size;i++) {
number[i]++;
if (number[i] < ALPHA_NUMBER_CHARS.length) {
break;
}
number[i]=0;
size = Math.max(i+1,size);
}
return toString();
}
public String toString() {
StringBuilder r = new StringBuilder();
for (int i = size; i>=0; i--) {
r.append(ALPHA_NUMBER_CHARS[number[i]]);
}
return new String(r);
}
public static void main(String[] args) {
AlphaNumber a = new AlphaNumber();
for (int i = 0; i < 100; i++) {
System.out.println(a.inc());
}
}
}