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@bufferings bufferings/Hello.java
Last active Aug 29, 2015

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public Result execute(Input in) {
checkNotNull(in, "In is null.");
try {
Integer productId = in.getSelected();
checkProductId(productId);
List<Integer> inputCoins = in.getCoins();
checkInputCoins(inputCoins);
Product product = dao.findById(productId);
checkArgument(product != null, "Product doesn't exist.");
return buyProduct(product, inputCoins);
} catch (Exception e) {
LOG.error(e);
return resultOf(in.getCoins());
}
}
void checkProductId(Integer aProductId) {
checkNotNull(aProductId, "ProductId must not be null.");
int productId = aProductId.intValue();
checkArgument(1 <= productId && productId <= 10,
"ProductId must be in the range 1-10.");
}
void checkInputCoins(List<Integer> aInputCoins) {
checkArgument(CollectionUtils.isNotEmpty(aInputCoins),
"InputCoins must not be null nor empty.");
checkArgument(aInputCoins.size() <= 100,
"InputCoins size must be up to 100.");
}
Result buyProduct(Product aProduct, List<Integer> aInputCoins) {
int sum = sumUpValidCoins(aInputCoins);
if (isShortOfMoney(sum, aProduct)) {
return resultOf(aInputCoins);
}
List<Integer> invalidCoins = getInvalidCoins(aInputCoins);
int change = sum - aProduct.getPrice();
List<Integer> changeCoins = getChangeCoins(change);
List<Integer> returnCoins = ListUtils.union(invalidCoins, changeCoins);
return resultOf(aProduct, returnCoins);
}
static final ImmutableSet<Integer> VALID_COINS = ImmutableSet.of(10, 50, 100, 500);
int sumUpValidCoins(List<Integer> aInputCoins) {
return aInputCoins.stream()
.filter(coin -> VALID_COINS.contains(coin))
.mapToInt(i -> i)
.sum();
}
boolean isShortOfMoney(int aSum, Product aProduct) {
return aSum < aProduct.getPrice();
}
List<Integer> getInvalidCoins(List<Integer> aInputCoins) {
return aInputCoins.stream()
.filter(coin -> not(VALID_COINS.contains(coin)))
.collect(Collectors.toList());
}
// お釣り計算のため、大きい順に並んでいる必要がある
static final ImmutableList<Integer> COINS_FOR_CHANGE = ImmutableList.of(500, 100, 50, 10);
List<Integer> getChangeCoins(int aChange) {
List<Integer> changeCoins = new ArrayList<>();
int rest = aChange;
for (Integer coin : COINS_FOR_CHANGE) {
while (rest > coin) {
changeCoins.add(coin);
rest -= coin;
}
}
return changeCoins;
}
Result resultOf(Product aProduct, List<Integer> aReturnCoins) {
Result result = new Result();
result.setProduct(aProduct);
result.setCoins(aReturnCoins);
return result;
}
Result resultOf(List<Integer> aInputCoins) {
Result result = new Result();
result.setProduct(null);
result.setCoins(aInputCoins);
return result;
}
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