@Repeatable注解的使用

package org.springmorning.demo.javabase.annotation.meta;

import java.lang.annotation.Repeatable;

@Repeatable(Schedules.class)
public @interface Schedule {
    String dayOfMonth() default "first";
    String dayOfWeek() default "Mon";
    int hour() default 12;
}

2.  再声明一个容器注解类

package org.springmorning.demo.javabase.annotation.meta;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface Schedules {
    Schedule[] value();
}

3. 创建一个测试类

package org.springmorning.demo.javabase.annotation.meta;

import java.lang.reflect.Method;

@Schedule(dayOfMonth="last")
@Schedule(dayOfWeek="Wed", hour=24)
public class RepetableAnnotation{

    @Schedule(dayOfMonth="last")
    @Schedule(dayOfWeek="Fri", hour=23)
    public void doPeriodicCleanup(){}

    public static void main(String[] args) throws NoSuchMethodException {

        Method doPeriodicCleanup = RepetableAnnotation.class.getMethod("doPeriodicCleanup");

        Schedules schedules = doPeriodicCleanup.getAnnotation(Schedules.class);
        System.out.println("获取标记方法上的重复注解：");
        for (Schedule schedule: schedules.value()){
            System.out.println(schedule);
        }

        System.out.println("获取标记类上的重复注解：");
        if (RepetableAnnotation.class.isAnnotationPresent(Schedules.class)){
            schedules = RepetableAnnotation.class.getAnnotation(Schedules.class);
            for (Schedule schedule: schedules.value()){
                System.out.println(schedule);
            }
        }

    }
}

运行结果：

获取标记方法上的重复注解：
@org.springmorning.demo.javabase.annotation.meta.Schedule(hour=12, dayOfMonth=last, dayOfWeek=Mon)
@org.springmorning.demo.javabase.annotation.meta.Schedule(hour=23, dayOfMonth=first, dayOfWeek=Fri)
获取标记类上的重复注解：
@org.springmorning.demo.javabase.annotation.meta.Schedule(hour=12, dayOfMonth=last, dayOfWeek=Mon)
@org.springmorning.demo.javabase.annotation.meta.Schedule(hour=24, dayOfMonth=first, dayOfWeek=Wed)

感兴趣的童鞋可以测试下~

以上，是Java面试题【@Repeatable注解的使用】的参考答案。

输出，是最好的学习方法。

欢迎在评论区留下你的问题、笔记或知识点补充~

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