Java基础之枚举Enum类案例详解

//格式：
 public enum 枚举名{ 
          //枚举的取值范围 
          //枚举中可以生命方法 
} 

public enum Day
{
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY,THURSDAY, FRIDAY, SATURDAY
}

public enum Season {
    SPRING,
    SUMMER,
    AUTUMN,
    WINTER;
}

//声明一个表示季节的枚举
public enum Season {
    SPRING,
    SUMMER,
    AUTUMN,
    WINTER;
}

public class TestSeasonEnum {
    public static void main(String[] args) {
        Season season = Season.SPRING;
        //switch小括号中的表达式类型可以是枚举类型
        switch(season){
            //每个case后的常量直接写枚举的取值范
        case SPRING:
            System.out.println("春天");
            break;
        case SUMMER:
            System.out.println("夏天");
            break;
        case AUTUMN:
            System.out.println("秋天");
            break;
        case WINTER:
            System.out.println("冬天");
            break;
        }
    }
}

public interface EnumInterface {
    public abstract void print();
}

public enum SizeEnum implements EnumInterface{
    BIG,MIDDLE,SMALL;

    @Override
    public void print() {
        System.out.println("继承接口-重写方法一次");
    }
}

public class InstanceDemo {

    /**
     * 构造方法私有化
     */
    private InstanceDemo(){

    }

    /**
     * 返回实例
     * @return
     */
    public static InstanceDemo getInstance() {
        return Singleton.INSTANCE.getInstance();
    }

    /**
     * 使用枚举方法实现单利模式
     */
    private enum Singleton {
        INSTANCE;

        private InstanceDemo instance;

        /**
         * JVM保证这个方法绝对只调用一次
         */
        Singleton() {
            instance = new InstanceDemo();
        }

        public InstanceDemo getInstance() {
            return instance;
        }
    }

//测试一下
    public static void main(String[] args) {
        InstanceDemo one =  InstanceDemo.getInstance();
        InstanceDemo two =  InstanceDemo.getInstance();
        System.out.println(one);
        System.out.println(two);
        System.out.println(one == two);
    }
}

csdn.test.recursion.demo.InstanceDemo@74a14482
csdn.test.recursion.demo.InstanceDemo@74a14482
true

 public final int compareTo(E o) {
        Enum<?> other = (Enum<?>)o;
        Enum<E> self = this;
        if (self.getClass() != other.getClass() && // optimization
            self.getDeclaringClass() != other.getDeclaringClass())
            throw new ClassCastException();
        return self.ordinal - other.ordinal;
    }

public class TestSeasonEnum {
    public static void main(String[] args) {
    
        Season season = Season.SPRING;
        Season season1 = Season.SUMMER;
        Season season2 = Season.AUTUMN;
        Season season3 = Season.WINTER;

        System.out.println(season.compareTo(season1));
        System.out.println(season.compareTo(season2));
        System.out.println(season.compareTo(season3));
    }
}