枚举类

//枚举类
public enum Size{SMALL,MEDIUM,LARGE,EXTRA_LARGE};
public static void main(String[] args) {

//for循环遍历枚举类型的所有实例
    for(Size s:Size.values()){
        System.out.println(s);
    }
}


栗子1

public class Main {
    public enum Operation{
        ADD{
            public  int eval(int arg1,int arg2){
                return arg1+arg2;
            }
        },
        SUBTRACT{
            public int eval(int agr1,int arg2){
                return agr1-arg2;
            }
        },
        MULTIPLY{
            public int eval(int arg1,int arg2){
                return arg1*arg2;
            }
        },
        DIVIDE{
            public int eval(int arg1,int arg2){
                return arg1/arg2;
            }
        };
　　　　　　//定义抽象方法
        public abstract int eval(int arg1,int arg2);
    }
    public static void main(String[] args) {
        Operation operation = Operation.ADD;
　　　　　　//自动寻找子类的实现
        int m = operation.eval(12,13);
        System.out.println(m);
        
    }

}

栗子2

package com.tech.Apple;

import jdk.nashorn.internal.ir.CallNode;

import javax.sound.midi.Soundbank;

public class Main {
    enum Operation{ADD,SUBTRACT,MULTIPLY,DIVIDE};
    public static int eval(Operation op,int agr1,int arg2){
        int result = 0;
        switch (op){
            case ADD:
                return result = agr1 + arg2;
            case SUBTRACT:
                return result = agr1-arg2;
            case MULTIPLY:
                return result = agr1*arg2;
            case DIVIDE:
                return result = agr1/arg2;
        }
        return result;
    }
    public static void main(String[] args) {
        int add_num = eval(Operation.ADD,12,13);
        System.out.println(add_num);
    }

}