java --- 枚举类

目录

一、枚举类

二、创建枚举类

2.1、JDK5.0之前创建 

 2.2、JDK5.0使用enum创建

 三、枚举类常用方法

 四、枚举类实现接口

一、枚举类

枚举类型本质上也是一种类，只不过是这个类的对象是有限的、固定的几个，不能让用户随意创建。

二、创建枚举类

2.1、JDK5.0之前创建 

public class SeasonTest {
    public static void main(String[] args) {
        System.out.println(Season.SPRING.getSeasonName());
    }
}
//JDK5.0之前创建方式
class Season{
    //定义属性
    private final String seasonName;
    private final String seasonDesc;
    //构造器私有化
    private Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    //提高get方法
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
    //创建当前类的实例
    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","白雪皑皑");

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

 2.2、JDK5.0使用enum创建

public class SeasonTest1 {
    public static void main(String[] args) {
        System.out.println(Season1.SPRING.getSeasonName());
    }
}
//JDK5.0创建方式
enum Season1{
    //创建当前类的实例
     SPRING("春天","春暖花开"),
     SUMMER("夏天","夏日炎炎"),
     AUTUMN("秋天","秋高气爽"),
     WINTER("冬天","白雪皑皑");
    //定义属性
    private final String seasonName;
    private final String seasonDesc;
    //构造器私有化
    private Season1(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
    //提高get方法
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

 三、枚举类常用方法

String toString(): 默认返回的是常量名（对象名），可以继续手动重写该方法！
   
static 枚举类型[] 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，是一个静态方法
   
static 枚举类型 valueOf(String name)：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”。如不是，会有运行时异常：IllegalArgumentException。
   
String name():得到当前枚举常量的名称。建议优先使用toString()。
   
int ordinal():返回当前枚举常量的次序号，默认从0开始

 //toString()
        System.out.println(Season1.SPRING);
        //name()
        System.out.println(Season1.SPRING.name());
        //values()
        Season1[] values = Season1.values();
        for (Season1 season1:values) {
            System.out.println(season1);
        }
        //valueOf():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”。
        // 如不是，会有运行时异常：IllegalArgumentException。
        System.out.println(Season1.valueOf("SPRING"));
        //ordinal()
        System.out.println(Season1.SUMMER.ordinal());

 四、枚举类实现接口

4.1、枚举的对象调用执行同一个方法

public class SeasonTest2 {
    public static void main(String[] args) {
        Season2.SPRING.method();
    }
}
interface Test01{
    public void method();
}
//JDK5.0创建方式
enum Season2 implements Test01{

    //创建当前类的实例
     SPRING("春天","春暖花开"),
     SUMMER("夏天","夏日炎炎"),
     AUTUMN("秋天","秋高气爽"),
     WINTER("冬天","白雪皑皑");
    @Override
    public void method() {
        System.out.println("实现接口成功");
    }
    //定义属性
    private final String seasonName;
    private final String seasonDesc;
    //构造器私有化
    private Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
}

4.2、枚举类的每个对象重写接口中的方法，执行每个对象重写的方法

public class SeasonTest2 {
    public static void main(String[] args) {
        Season2[] values = Season2.values();
        for (int i = 0; i < values.length; i++) {
            values[i].method();
        }
    }
}
interface Test01{
    public void method();
}
//JDK5.0创建方式
enum Season2 implements Test01{

    //创建当前类的实例
     SPRING("春天","春暖花开"){
        @Override
        public void method() {
            System.out.println("春天重写接口方法");
        }
    },
     SUMMER("夏天","夏日炎炎"){
         @Override
         public void method() {
             System.out.println("夏天重写接口方法");
         }
     },
     AUTUMN("秋天","秋高气爽"){
         @Override
         public void method() {
             System.out.println("秋天重写接口方法");
         }
     },
     WINTER("冬天","白雪皑皑"){
         @Override
         public void method() {
             System.out.println("冬天重写接口方法");
         }
     };
//    @Override
//    public void method() {
//        System.out.println("实现接口成功");
//    }
    //定义属性
    private final String seasonName;
    private final String seasonDesc;
    //构造器私有化
    private Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
}