Java无法解析嵌套的json对象

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonParser {
    public static void main(String[] args) {
        String json = "{\"name\":\"John\",\"age\":30,\"address\":{\"city\":\"New York\",\"country\":\"USA\"}}";

        try {
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode rootNode = objectMapper.readTree(json);

            String name = rootNode.get("name").asText();
            int age = rootNode.get("age").asInt();
            String city = rootNode.get("address").get("city").asText();
            String country = rootNode.get("address").get("country").asText();

            System.out.println("Name: " + name);
            System.out.println("Age: " + age);
            System.out.println("City: " + city);
            System.out.println("Country: " + country);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}