Java学习笔记（尚硅谷，枚举类与注解）_尚硅谷 java 注解-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_52354687/article/details/118565535

本文详细介绍了Java中的枚举类两种实现方式，包括自定义枚举类和使用`enum`关键字，并展示了如何实现接口。同时，讨论了JDK8之前的可重复注解与JDK8的新特性，以及自定义注解和元注解的概念。通过实例展示了如何在代码中使用这些特性。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

枚举类

自定义枚举类

public class SeasonTest {
    public static void main(String[] args) {
        Season autumn = Season.AUTUMN;
        System.out.println(autumn);
    }
}

class Season {
    private final String SeasonName;
    private final String SeasonDesc;

    public Season(String seasonName, String seasonDesc) {
        SeasonName = seasonName;
        SeasonDesc = seasonDesc;
    }

    public static final Season SPRING = new Season("春天", "春暖花开");
    public static final Season SUMMER = new Season("夏天", "夏日炎炎");
    public static final Season AUTUMN = new Season("秋天", "秋高气爽");
    public static final Season WINTER = new Season("冬天", "天寒地冻");

    public String getSeasonName() {
        return SeasonName;
    }

    public String getSeasonDesc() {
        return SeasonDesc;
    }

    @Override
    public String toString() {
        return "Season{" +
                "SeasonName='" + SeasonName + '\'' +
                ", SeasonDesc='" + SeasonDesc + '\'' +
                '}';
    }
}

enum定义枚举类

在这里插入图片描述

public class EnumTest {
    public static void main(String[] args) {
    	// 获取所有枚举类的所有对象构成的数组
        Season1[] values = Season1.values();
        for (int i = 0; i < values.length; i++) {
            System.out.println(values[i]);
            values[i].show();
        }
		// 根据字符串返回枚举对象
        Season1 spring = Season1.valueOf("SPRING");
        System.out.println(spring);
    }
}

interface Info {
    void show();
}

enum Season1 implements Info {
	// 枚举类实现接口的一种方式
    SPRING("春天", "春暖花开") {
        @Override
        public void show() {

        }
    },

    SUMMER("夏天", "夏日炎炎") {
        @Override
        public void show() {

        }
    },
    AUTUMN("秋天", "秋高气爽") {
        @Override
        public void show() {

        }
    },
    WINTER("冬天", "天寒地冻") {
        @Override
        public void show() {

        }
    };

    private final String seasonName;
    private final String seasonDesc;

    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    Season1(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
}

注解

在这里插入图片描述

自定义注解

在这里插入图片描述

public @interface MyAnnotation {
    String value() default "hello"; // 默认值 hello
}

@MyAnnotation(value = "hello world")
class MyTest {

}

元注解

在这里插入图片描述

JDK8新特性

可重复注解

JDK8以前

public @interface MyAnnotation {
    String value() default "hello"; // 默认值 hello
}

public @interface MyAnnotations {
    MyAnnotation[] value();
}

@MyAnnotations({@MyAnnotation(value = "a"), @MyAnnotation(value = "b")})
class MyTest {

}

JDK8以后

@Repeatable(MyAnnotations.class)
public @interface MyAnnotation {
    String value() default "hello"; // 默认值 hello
}

public @interface MyAnnotations {
    MyAnnotation[] value();
}

@MyAnnotation(value = "a")
@MyAnnotation(value = "b")
class MyTest {

}