How can I validate a collection as empty in Jakarta Validation?

How can I validate a collection is empty?

    // should be empty!
    @JsonbTransient
    @JsonIgnore
    @XmlAnyAttribute
    private Map<QName, Object> unknownAttributes;

    // should be empty!
    @JsonbTransient
    @JsonIgnore
    @XmlAnyElement
    private List<Element> unknownElements;

I know @NotEmpty can help for apposite validation.

I currently doing this.

    @AssertTrue(message = "unknown attributes should be empty")
    private boolean isUnknownAttributesEmpty() {
        if (unknownAttributes == null) {
            return true;
        }
        return unknownAttributes.isEmpty();
    }

    @AssertTrue(message = "unknown elements should be empty")
    private boolean isUnknownElementsEmpty() {
        if (unknownElements == null) {
            return true;
        }
        return unknownElements.isEmpty();
    }

Is there any good way to do this? Why there is no @Empty, or is there?

jakarta.validation.constraints.Size

You can use @Size as Jakarta Validation annotation to validate the size of a collection, map, array or charSequence.