java統計實體類中空欄位數量

package org.example;
import java.lang.reflect.Field;
/**
 * @author 50649
 */
public class TestCount {
    public static int countNullFields(Object entity) throws IllegalAccessException {
        if (entity == null) {
            return 0;
        }
        int nullFieldCount = 0;
        Class<?> clazz = entity.getClass();
        Field[] fields = clazz.getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true);
            Object fieldValue = field.get(entity);
            if (fieldValue == null) {
                nullFieldCount++;
            }
        }
        return nullFieldCount;
    }

    public static void main(String[] args) throws IllegalAccessException {
        // 假設有一個實體類 Entity 如下：
        // class Entity {
        //     String name;
        //     Integer age;
        //     String email;
        // }
        Entity entity = new Entity();
        entity.name = "John";
        entity.email = null;

        int nullFieldCount = countNullFields(entity);
        System.out.println("Number of null fields: " + nullFieldCount);
    }
}

　　

package org.example;

/**
 * @author 50649
 */
public class Entity {
    String name;
    Integer age;
    String email;
}