effective 2

用枚举代替单例模式

高效而且安全

public enum Singleton {
    SINGLETON;

    public String say(){
        return "hello";
    }

    public static void main(String[] args) {
       String s = SINGLETON.say();
        System.out.println(s);
    }

}

用枚举代理int常量

清晰而且安全

public class Demo01 {

    public static void main(String[] args) {
        System.out.println(APPLE1.getAge());
    }

}

class Fruit{
    public static final int APPLE1 = 1;
    public static final int APPLE2 = 2;
    public static final int PEAR1 = 1;
    public static final int PEAR2 = 2;

}

enum Apple {
    APPLE1(1), APPLE2(2);
    private int age;

    public int getAge() {
        return age;
    }

    private Apple(int age) {
        this.age = age;
    }
}

enum Pear {
    PEAR1(1), PEAR2(2);
    private int age;

    public int getAge() {
        return age;
    }

    private Pear(int age) {
        this.age = age;
    }
}

用枚举代替各种状态

清晰,高效,安全

public enum EntryStatus implements DescEnum {
    INIT(0,"初始"),
    VALIDATED(1, "已生效"),
    NOTPASSED(2,"审核未通过"),
    ;
    private int code;
    private String desc;

    EntryStatus(int status,String desc) {
        this.code = status;
        this.desc = desc;
    }

    @Override
    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    @Override
    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }
}