自动售货机的找零程序模拟
模拟自动售货机的找零程序。需求描述如下：
1、程序根据用户投入货币的面额及其数量，在扣除购买的商品价额后，进行找零。
2、程序需要根据售货机内现存的各种货币面额和数量，在优先分配大面额货币的条件下，进行找零。
3、暂时仅支持整数找零。
4、实际的自动售货机找零是串行化操作，因此不考虑多线程同步问题。
package org.tang.change;
/**
* 货币枚举类
* @author Tang
*
*/
public enum Currency {
/**
* 货币面额
*/
HUNDRED_YUAN(100),
FIFTY_YUAN(50),
TWENTY_YUAN(20),
TEN_YUAN(10),
FIVE_YUAN(5),
ONE_YUAN(1);
/**
* 货币面额值
*/
private int value;
public int getValue() {
return value;
}
private Currency(int value){
this.value = value;
}
}
定义货币面额的枚举类。在需要增加面额情况下，可以扩展词枚举类。但是需要保证按照面额降序排列，这是为了实现较大面额货币将被优先分配找零的目的。
package org.tang.change;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* 自动售货机类
* @author Tang
*
*/
public class VendingMachine {
private static final VendingMachine MACHINE = new VendingMachine();
/**
* key表示货币面额
* value表示该面额货币在此售货机当中的存量
*/
private static Map<Currency, Integer> moneyPool = new HashMap<Currency, Integer>();
private static Log logger = LogFactory.getLog(VendingMachine.class);
static {
initMoneyPool();
}
private VendingMachine(){}
/**
* 返回自动售货机实例
* @return
*/
public static VendingMachine getInstance(){
return MACHINE;
}
/**
* 初始化零钱库存
*/
private static void initMoneyPool(){
moneyPool.put(Currency.ONE_YUAN, 4);
moneyPool.put(Currency.FIVE_YUAN, 8);
moneyPool.put(Currency.TEN_YUAN, 5);
moneyPool.put(Currency.TEN_YUAN, 5);
moneyPool.put(Currency.TWENTY_YUAN, 3);
moneyPool.put(Currency.FIFTY_YUAN, 2);
moneyPool.put(Currency.HUNDRED_YUAN, 0);
if(logger.isInfoEnabled()){
logger.info("初始化售货机零钱库量："+getStockBalance());
}
}
/**
* 将收到的钱放入零钱库
*/
private void put(Map<Currency,Integer> putMap){
if(logger.isInfoEnabled()){
logger.info("put操作前零钱库存量："+getStockBalance());
}
for(Map.Entry<Currency, Integer> entry : putMap.entrySet()){
Integer count = moneyPool.get(entry.getKey());
moneyPool.put(entry.getKey(),(count == null ? 0:count) + entry.getValue());
}
if(logger.isInfoEnabled()){
logger.info("put操作后零钱库存量："+getStockBalance());
}
}
/**
* 从零钱库中取出若干零钱
* @param takeMap
*/
private void take(Map<Currency,Integer> takeMap){
if(logger.isInfoEnabled()){
logger.info("take操作前零钱库存量："+getStockBalance());
}
for(Map.Entry<Currency, Integer> entry : takeMap.entrySet()){
Integer count = moneyPool.get(entry.getKey());
moneyPool.put(entry.getKey(),(count == null ? 0:count) - entry.getValue());
}
if(logger.isInfoEnabled()){
logger.info("take操作后零钱库存量："+getStockBalance());
}
}
/**
* 返回当前库中零钱总额
* @return
*/
public static int getStockBalance() {
return Currency.ONE_YUAN.getValue() * moneyPool.get(Currency.ONE_YUAN)
+ Currency.FIVE_YUAN.getValue()
* moneyPool.get(Currency.FIVE_YUAN)
+ Currency.TEN_YUAN.getValue()
* moneyPool.get(Currency.TEN_YUAN)
+ Currency.TWENTY_YUAN.getValue()
* moneyPool.get(Currency.TWENTY_YUAN)
+ Currency.FIFTY_YUAN.getValue()
* moneyPool.get(Currency.FIFTY_YUAN)
+ Currency.HUNDRED_YUAN.getValue()
* moneyPool.get(Currency.HUNDRED_YUAN);
}
/**
* 找零钱
* @return
*/
public Map<Currency,Integer> giveChange(int cost, Map<Currency,Integer> putMap) {
if(putMap == null){
throw new NullPointerException();
}
int putAmount = getPutAmount(putMap);
int payAmount = putAmount - cost;
if(logger.isInfoEnabled()){
logger.info("您需要为商品支付"+cost+"元，现收您"+putAmount+"元，还需找您"+payAmount+"元。");
}
if(cost <= 0 || putAmount == 0 || payAmount < 0){
throw new IllegalArgumentException("您的入参错误");
}
put(putMap);
Map<Currency,Integer> rtMap = new HashMap<Currency,Integer>(2);
for(Currency cur : Currency.values()){
if(payAmount == 0){
break;
}
Integer count = moneyPool.get(cur);
if(count == null){
continue;
}
if(payAmount - cur.getValue() == 0){
rtMap.put(cur, 1);
payAmount = 0;
break;
}
if(payAmount - cur.getValue() > 0 && payAmount / cur.getValue() > 0 && count >= (payAmount / cur.getValue())){
rtMap.put(cur, payAmount / cur.getValue());
payAmount = payAmount % cur.getValue();
}
}
if(payAmount != 0){
take(putMap);
throw new IllegalStateException("自动售货机零钱不够了。。。您的钱将自动退还");
}
take(rtMap);
return rtMap;
}
/**
* 返回收到的总金额
* @return
*/
private int getPutAmount(Map<Currency,Integer> putMap){
if(putMap == null || putMap.isEmpty()){
return 0;
}
int val = 0;
for(Map.Entry<Currency,Integer> entry : putMap.entrySet()){
val += entry.getKey().getValue()*entry.getValue();
}
return val;
}
}
package org.tang.change;
import java.util.HashMap;
import java.util.Map;
public class Client {
/**
* @param args
*/
public static void main(String[] args) {
Map<Currency,Integer> map = new HashMap<Currency,Integer>();
//投入售货机1张50元钞
map.put(Currency.FIFTY_YUAN, 1);
//需要为商品支付金额
int cost = 31;
VendingMachine machine = VendingMachine.getInstance();
Map<Currency,Integer> rtMap = machine.giveChange(cost,map);
System.out.println("\r自动售货机找零情况如下：");
for(Map.Entry<Currency, Integer> entry : rtMap.entrySet()){
System.out.println(entry.getValue()+"张"+entry.getKey().getValue()+"元");
}
}
}
INFO 2012-10-23 20:10:35,718 org.tang.change.VendingMachine: 初始化售货机零钱库量：254 INFO 2012-10-23 20:10:35,720 org.tang.change.VendingMachine: 您需要为商品支付30元，现收您50元，还需找您20元。 INFO 2012-10-23 20:10:35,721 org.tang.change.VendingMachine: put操作前零钱库存量：254 INFO 2012-10-23 20:10:35,721 org.tang.change.VendingMachine: put操作后零钱库存量：304 INFO 2012-10-23 20:10:35,722 org.tang.change.VendingMachine: take操作前零钱库存量：304 INFO 2012-10-23 20:10:35,722 org.tang.change.VendingMachine: take操作后零钱库存量：284 自动售货机找零情况如下： 1张20元