一.列舉

在JDK1.5之前，我們定義常量都是：public static final....。現在好了，有了列舉，可以把相關的常量分組到一個列舉型別裡，而且列舉提供了比常量更多的方法。

public class Season {
    public static final Season SPRING=new Season("春天","穿暖花開");
    public static final Season SUMMER=new Season("夏天","烈日炎炎");
    public static final Season AUTUMN=new Season("秋天","天高雲闊");
    
 
public static final Season WINTER=new Season("冬天","白雪皚皚");

    private String name;
    private String des;
    private Season(){};

    private Season(String name, String des) {
        this.name = name;
        this.des = des;
    }

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

版本迭代以後

1.構造器預設私有

2.列舉中屬性必須位於列舉元素下面

3.所有的自定義列舉預設繼承自Enum類

public enum Season {
    SPRING("春天","穿暖花開"),
    SUMMER("夏天","烈日炎炎"),
    AUTUMN("秋天","天高雲闊"),
    WINTER("冬天","白雪皚皚");

    private String name;
    private String des;
    Season(){};

    Season(String name, String des) {
        this.name = name;
        
 
this.des = des;
    }
    
}

也可以直接建立一個Enum型別

public enum Gender {
    MAN,WOMAN
}

main

public class EnumTest {
    public static void main(String[] args) {
        Gender gender=Gender.MAN;
        switch (gender){
            case MAN:
                System.out.println("just man");
                break;
            case WOMAN:
                System.out.println("just woman");
                break;
            default:
                throw new IllegalStateException("Unexpected value: " + gender);
        }
    }
}

即可