一文了解Java中枚举的使用

// 简单的定义
enum WeekEnum {
    MONDAY, TUESDAY
}

// 有属性的定义
enum StatusEnum {
    ENABLE("1", "启用"), DISABLE("0", "禁用");

    private String code;

    private String name;

    StatusEnum(String code, String name) {
        this.code = code;
        this.name = name;
    }
}

public static void main(String[] args) {
        // 根据字符串获取枚举
        StatusEnum enable = Enum.valueOf(StatusEnum.class, "ENABLE");
        System.out.println(enable);
        //枚举比较直接用==
        System.out.println(enable == StatusEnum.ENABLE);

        // values方法获取所有的枚举
        StatusEnum[] values = StatusEnum.values();
        for (StatusEnum statusEnum : values) {
            // 打印枚举的位置
            System.out.println(statusEnum.ordinal());
        }
    }

public class User {
    //私有化构造函数
    private User(){ }
 
    //定义一个静态枚举类
    static enum SingletonEnum{
        //创建一个枚举对象，该对象天生为单例
        INSTANCE;
        private User user;
        //私有化枚举的构造函数
        private SingletonEnum(){
            user = new User();
        }
        public User getInstnce(){
            return user;
        }
    }
 
    //对外暴露一个获取User对象的静态方法
    public static User getInstance(){
        return SingletonEnum.INSTANCE.getInstnce();
    }
}

enum OperEnum {
    ADD(1, 2) {
        @Override
        public Integer operate() {
            return this.getA() + this.getB();
        }
    }, MULTIPY(1, 2) {
        @Override
        public Integer operate() {
            return this.getA() * this.getB();
        }
    };

    private Integer a;

    private Integer b;

    OperEnum(Integer a, Integer b) {
        this.a = a;
        this.b = b;
    }

    public abstract Integer operate();

    public Integer getA() {
        return a;
    }

    public void setA(Integer a) {
        this.a = a;
    }

    public Integer getB() {
        return b;
    }

    public void setB(Integer b) {
        this.b = b;
    }
}