Rest API- how to filter a response from a Json body - How to count number of people, whose age equals certain number?

Question

I am doing a get request which returns me a large number of employees. How do I filter after a certain condition, how to count the number for the employees that are older than a certain age, in the REST API for cucumber?

e.g.

"data": [
        {
            "id": 1,
            "employee_name": "Tiger Nixon",
            "employee_salary": 320800,
            "employee_age": 20,
            "profile_image": ""
        },
        {
            "id": 2,
            "employee_name": "Garrett Winters",
            "employee_salary": 170750,
            "employee_age": 63,
            "profile_image": ""
        },
        {
            "id": 3,
            "employee_name": "Ashton Cox",
            "employee_salary": 86000,
            "employee_age": 66,
            "profile_image": ""
        }]

I do not know how to count in a response from employee_age.

@Test
public void givenJson_whenParseObject_thenGetSize() {

    assertThat(jsonObject)
        .size()  - but how to filter on the age?
}