import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;

public class AnnotationPractice {
    public static void main(String[] args) throws IllegalAccessException {
        City city = new City("重庆", "重庆不夜城", 3000);
        check(city);
    }

    static void check(City city) throws IllegalAccessException {
        for (Field field : city.getClass().getFields()) {
            Range range = field.getAnnotation(Range.class);
            if (range == null) {
                continue;
            }
            Object value = field.get(city);
            int number = value instanceof String s ?
                    s.length() :
                    value instanceof Integer years ? years : -1;
            if (number != -1)
                isIn(range.min(), range.max(), number, field);
        }
    }

    static void isIn(int leftNum, int rightNum, int number, Field field) {
        if (number < leftNum || number > rightNum) {
            throw new IllegalArgumentException("Invalid field: " + field.getName());
        }

    }
}


class City {
    @Range(min = 2, max = 20)
    public String cityName;
    @Range(min = 1, max = 50)
    public String citySongName;

    @Range(min = 1, max = 10000)
    public float YearsOfHistory;

    public City(String cityName, String citySongName, int yearsOfHistory) {
        this.cityName = cityName;
        this.citySongName = citySongName;
        YearsOfHistory = yearsOfHistory;
    }
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Range {
    int min() default 0;

    int max() default 255;
}