Java enum实现自增赋值方式

enum MSG_TYPE {
    MSG_LOGIN = 500,
    MSG_LOGOUT,
    MSG_REGISTER,
    MSG_SEARCH,
    /* ... */
};

public enum MSG_TYPE{
    MSG_LOGIN(500),
    MSG_LOGOUT(501),
    MSG_REGISTER(502),
    MSG_SEARCH(503),
    /* ... */
    MSG_ADD(600);
    
    private int egId;
    private MSG_TYPE(int val){
        this.egId = val
    }
    
    public getEgId(){
        return this.egId;
    }
}

import java.util.EnumSet;
 
public class EnumTest {
    public static void main(String[] args) {
        for (MSG_TYPE msg_type : EnumSet.allOf(MSG_TYPE.class))
        {
            System.out.println(msg_type.name() + " " +
                    msg_type.ordinal() + " " +
                    msg_type.getValue());
        }
    }
}
 
enum MSG_TYPE {
    MSG_LOGIN(500),
    MSG_LOGOUT,
    MSG_REGISTER,
    MSG_SEARCH,
    MSG_ADD(600);
 
    private int value;
    private static int nextValue;
    MSG_TYPE(){
        this(Counter.nextValue);
    }
    MSG_TYPE(int value){
        this.value = value;
        Counter.nextValue = value + 1;
    }
 
    public int getValue()
    {
        return value;
    }
 
    private static class Counter
    {
        private static int nextValue = 0;
    }
}

#include<stdio.h>

enum {a, b, c, d=9, e}day1,day2;

int main()
{
	int day;
	day1=b;
	day2=e;
	day=day1+day2;
    printf("%d\t",day);
    
    return 0;
}