Thinking In Java学习笔记之enum状态机

输入的枚举：

package com;

import java.util.Random;

public enum Input{
	NICKEL(5),DIME(10),QUARTER(25),DOLLAR(100),TOOTHPASTE(200),CHIPS(75),SODA(100)
	,SOAP(50),
	ABORT_TRANSACTION{
		public int amount(){
			throw new RuntimeException("Abort exception");
		}
	},
	STOP{
		public int amount(){
			throw new RuntimeException("ShutDown exception");
		}
	};
	int value;
	Input(){}
	Input(int v){
		this.value=v;
	}
	public int amount(){
		return value;
	}
	static Random rand=new Random(47);
	public static Input randomSelection(){
		return values()[rand.nextInt(values().length-1)];
	}
}

package com;

import java.util.EnumMap;
import java.util.Random;

import static com.Input.*;	//可以把enum下的所有常量引入直接使用

public class VendingMachine {
	private static State state=State.RESTING;
	private static int amount;
	private static Input selection=null;
	enum StateDuration{TRANSIENT}
	enum State{
		RESTING{	//定义个性的方法
			void next(Input input){
				switch(Category.categorize(input)){
				case MONEY:
					amount+=input.amount();
					state=ADDING_MONEY;
					break;
				case SHUT_DOWN:
					state=TERMINAL;
					default:
				}
			}
		},
		ADDING_MONEY{
			void next(Input input){
				switch(Category.categorize(input)){
				case MONEY:
					amount+=input.amount();
					break;
				case ITEM_SELECTION:
					selection=input;
					if(amount0){
					System.out.println("Your change: "+amount);
					amount=0;
				}
				state=RESTING;
			}
		},
		TERMINAL{
			void output(){
				System.out.println("Halted");
			}
		};
		private boolean isTransient=false;
		State(){}
		State(StateDuration sd){
			isTransient=true;
		}
		void next(Input input){	//公共方法
			throw new RuntimeException("Only call next(Input input) for "
					+"non-transient states");
		}
		void next(){
			throw new RuntimeException("Only call next() for "
					+"non-transient states");
		}
		void output(){
			System.out.println(amount);
		}
	}
	public static void run(Generator gen){
		while(state!=State.TERMINAL){
			state.next((Input) gen.next());	//枚举类型持有方法
			while(state.isTransient)
				state.next();
			state.output();
		}
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Generator gen=new RandomInputGenerator();
		run(gen);
	}

}
interface Generator{
	public T next();
}
class RandomInputGenerator implements Generator{
	@Override
	public Input next() {
		return Input.randomSelection();
	}
}
enum Category{
	MONEY(NICKEL,DIME,QUARTER,DOLLAR),//初始化
	ITEM_SELECTION(TOOTHPASTE,CHIPS,SODA,SOAP),
	QUIT_TRANSACTION(ABORT_TRANSACTION),
	SHUT_DOWN(STOP)
	;
	private Input[] values;
	Category(Input ... types){
		values=types;	//初始化获取Input列表
	}
	static EnumMap categories=new EnumMap(Input.class);
	static{
		for(Category c: Category.class.getEnumConstants()){	//获取所有常量，遍历每个常量的初始化之后的数组，并保存起来
			for(Input in: c.values){
				categories.put(in, c);//对另一个enum进行分类
			}
		}
	}
	public static Category categorize(Input input){
		return categories.get(input);
	}
}