Here is an example of using the ConstructorDetector class from the com.fasterxml.jackson.databind package in the Jackson library for Java:

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.cfg.ConstructorDetector;

public class Example {
    public static void main(String[] args) {
        // create a new ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        // get the ConstructorDetector of the mapper
        ConstructorDetector constructorDetector = mapper.getDeserializationConfig().getConstructorDetector();
        
        // example input JSON string
        String jsonInput = "{\"name\":\"John\",\"age\":30}";
        try {
            // use the ObjectMapper to deserialize the input JSON to a Person object
            Person person = mapper.readValue(jsonInput, Person.class);
            System.out.println("Person: " + person);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class Person {
    private final String name;
    private final int age;

    @JsonCreator
    public Person(@JsonProperty("name") String name, @JsonProperty("age") int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + "]";
    }
}

This example uses the ConstructorDetector class to find and use the constructor annotated with @JsonCreator and @JsonProperty to deserialize JSON input to a Person object. The ConstructorDetector is used to find the @JsonCreator constructor, and the @JsonProperty annotations are used to map the JSON properties to the constructor arguments.