自定义枚举类

在 JDK 5.0 之前，我们需要自定义枚举类

public class EnumerateTest {
    public static void main(String[] args) {
        Season spring = Season.SPRING;
        System.out.println(spring);
    }
}
//自定义枚举类：四季
class Season{
    //1. 声明 Season 对象的属性：private final 修饰
    private final String seasonName;
    private final String seasonDesc;
    //2. 私有化类的构造器，并给对象属性赋值
    private Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    //3. 提供当前枚举类的多个对象：private static final 修饰
    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","冬日夏云");
    //其他：获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }
    //其他：提供toString()
    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + '\'' +
                ", seasonDesc='" + seasonDesc + '\'' +
                '}';
    }
}

>>> Season{seasonName='春天', seasonDesc='春暖花开'}

关键字enum定义枚举类

在 JDK 5.0 及之后，我们可以使用 enum 关键字来定义枚举类

public class EnumerateTest {
    public static void main(String[] args) {
        Season spring = Season.SPRING;
        System.out.println(spring);
    }
}
//enum关键字定义枚举类：四季
enum  Season{
    //1. 提供当前枚举类的对象，多个对象之间用 “,” 隔开，末尾对象 “;” 结束
        SPRING ("春天","春暖花开"),
        SUMMER ("夏天","夏日炎炎"),
        AUTUMN ("秋天","秋高气爽"),
        WINTER ("冬天","冬日夏云");
    //2. 声明 Season 对象的属性：private final 修饰
    private final String seasonName;
    private final String seasonDesc;
    //3. 私有化类的构造器，并给对象属性赋值
    private Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    //其他：获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }
    //其他：提供toString()
    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + '\'' +
                ", seasonDesc='" + seasonDesc + '\'' +
                '}';
    }
}

>>> Season{seasonName='春天', seasonDesc='春暖花开'}

enum类的主要方法

values（）	返回枚举类型的对象数组。该方法可以很方便地遍历所有的枚举值
valueOf（String str）	可以把一个字符串转为对应的枚举类对象。要求字符串必须是枚举类对象的 “名字” 。如果不是，会有运行时异常
toString（）	返回当前枚举类对象常量的名称

public class EnumerateTest {
    public static void main(String[] args) {
        Season spring = Season.SPRING;
        //toString()
        System.out.println(spring.toString());
        System.out.println("************");
        //values()
        Season[] values = Season.values();
        for (int i = 0; i < values.length; i++) {
            System.out.println(values[i]);
        }
        System.out.println("************");
        Thread.State[] values1 = Thread.State.values();
        for (int i = 0; i < values1.length; i++) {
            System.out.println(values1[i]);
        }
        System.out.println("************");
        //valueOf()
        Season winter = Season.valueOf("WINTER");
        System.out.println(winter);
    }
}
enum Season{
    //与上一个代码块代码相同
}

>>> Season{seasonName='春天', seasonDesc='春暖花开'}
    ************
    Season{seasonName='春天', seasonDesc='春暖花开'}
    Season{seasonName='夏天', seasonDesc='夏日炎炎'}
    Season{seasonName='秋天', seasonDesc='秋高气爽'}
    Season{seasonName='冬天', seasonDesc='冬日夏云'}
    ************
    NEW
    RUNNABLE
    BLOCKED
    WAITING
    TIMED_WAITING
    TERMINATED
    ************
    Season{seasonName='冬天', seasonDesc='冬日夏云'}

enum关键字定义枚举类实现接口

实现接口，可以在 enum 类中实现抽象方法，也可以让枚举类的对象分别实现接口中的抽象方法

public class EnumerateTest {
    public static void main(String[] args) {
        Season winter = Season.valueOf("WINTER");
        winter.show();
    }
}
interface Info{
    void show();
}
//enum关键字定义枚举类：四季
enum  Season implements Info{
        SPRING ("春天","春暖花开"){
        @Override
        public void show() {
            System.out.println("春天来了");
            }
        },
        SUMMER ("夏天","夏日炎炎"){
            @Override
            public void show() {
                System.out.println("夏天来了");
            }
        },
        AUTUMN ("秋天","秋高气爽"){
            @Override
            public void show() {
                System.out.println("秋天来了");
            }
        },
        WINTER ("冬天","冬日夏云"){
            @Override
            public void show() {
                System.out.println("冬天来了");
            }
        };
}

>>> 冬天来了