Java第九章枚举&注解

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)

 

 

4.利用反射获取注解信息(在反射部分涉及)