any annotations for a field which is like db generated sequence in JAVA

I have a scenario where there is a DB column which should be like sequence for each primary key + another column. The column's value should again reset and start from 1 for another.

For example:

col1(PK)------col2(FK)-------my-column

0---------------0-------------------1

1---------------0-------------------2

2---------------0-------------------3

3---------------1-------------------1

4---------------1-------------------2

5---------------1-------------------3

For col1(PK), I can simply annotate with @GeneratedValue(strategy = GenerationType.IDENTITY)

In the same way, I want to generate value for my-column as well.

From the code side, This is what it looks like:

classA{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private String col2;
    @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "classa", orphanRemoval = true)
    private List<ClassB> listB = new ArrayList<>();

    //I want to generate/increment the value of myCol each time based on value of col1 & col2
    @Column(name = "my-col")
    private Integer myCol;
//getter/setters
}

ClassB{
    @Id
    @Column(name = "col1")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer col1;

    @ManyToOne
    @JoinColumn(name = "col2")
    private ClassA classa;

//getter/setter
}