Java第九章枚举&注解

最新推荐文章于 2024-12-12 23:41:36 发布

转载最新推荐文章于 2024-12-12 23:41:36 发布 · 127 阅读

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/yangHS/p/10699727.html

本文深入探讨了枚举和注解在Java中的应用。详细介绍了如何自定义枚举类，包括属性声明、构造器使用、对象创建及方法实现。同时，解析了JDK内置注解类型及其用途，如@Override、@Deprecated和@SuppressWarnings，并展示了如何创建自定义注解。

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九、枚举&注解

枚举：

　　自定义枚举类

//枚举类
class Season{
    //1.提供类的属性，声明为private final
    private final String seasonName;
    private final String seasonDesc;
    //2.声明为final的属性，在构造器中初始化
    private Season(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    //3.通过公共的方法来调用属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }
    //4.创建枚举类的对象：将类的对象声明public static final
    public static final Season SPRING = new Season("spring","春暖花开");
    public static final Season SUMMER = new Season("summer","夏日炎炎");
    public static final Season AUTOMN = new Season("autumn","秋高气爽");
    public static final Season WINTER = new Season("winter","白雪皑皑");
    @Override
    public String toString() {
        return "Season [seasonName=" + seasonName + ", seasonDesc="
                + seasonDesc + "]";
    }
    public void show(){
        System.out.println("这是一个季节");
    }

　　enum关键字定义枚举类

　　常用的方法：value() valueOf(String name)

    1.values()
    Season1[] season = Season1.values();
    for(int i = 0;i < season.length;i++){
        System.out.println(season[i]);
    }
    2.valueOf(String name):要求传入的形参name是枚举类对象的名字
    String str = "SPRING";
    Season1 sea =  Season1.valueOf(str);

　　让枚举类是实现接口：可以让不同的枚举类的对象调用被重写的抽象方法，执行的效果不同

enum Season extends ss{
    SPRING("spring","春暖花开"){
        public void show(){
            System.out.println("春天");
        }
    },
    SUMMER("summer","夏日炎炎"){
        public void show(){
            System.out.println("夏天");
        }
    },
    AUTOMN("autumn","秋高气爽"){
        public void show(){
            System.out.println("秋天");
        }
    },
    WINTER("winter","白雪皑皑"){
        public void show(){
            System.out.println("冬天");
        }
    };
    private String seasonName;
    private String seasonDesc;
    private Season(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }
    public String toString() {
        return "Season [seasonName=" + seasonName + ", seasonDesc="
                + seasonDesc + "]";
    }

注解annotation

1.JDK内置的基本注解类型（3个）

@Override:限定重写父类的方法，该注释只能用于方法

@Deprecated：用于表示某个程序元素(类，方法等)已过时

@SuppressWarnings:抑制编译器警告

2.自定义注解类型

public @interface XX{
String value() default "hellow";
}
@XX(value = "xxx")

3.对注解进行注解(4个)(原注解)