public static <T> void show(String title, Stream<T> stream) {
final int SIZE = 10;
List<T> firstElements = stream.limit(SIZE + 1).collect(Collectors.toList());
System.out.print(title + ": ");
if (firstElements.size() <= SIZE) System.out.println(firstElements);
else {
firstElements.remove(SIZE);
String out = firstElements.toString();
System.out.println(out.substring(0, out.length() - 1) + ", ...]");
}
}
public class BestPriceFinder {
private final List<Shop> shops =
Arrays.asList(
new Shop("BestPrice"),
new Shop("LetsSaveBig"),
new Shop("MyFavoriteShop"),
new Shop("BuyItAll"),
new Shop("ShopEasy"));
private final Executor executor =
Executors.newFixedThreadPool(
shops.size(),
new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setDaemon(true);
return t;
}
});
/*
public List<String> findPriceSequential(String product) {
return shops.stream()
.map(shop -> shop.getName() + " price is " + shop.calculatePrice(product))
.collect(Collectors.<String>toList());
}
public List<String> findPriceParallel(String product) {
return shops.parallelStream()
.map(shop -> shop.getName() + " price is " + shop.calculatePrice(product))
.collect(Collectors.<String>toList());
}
public List<String> findPrice(String product) {
List<CompletableFuture<String>> priceFutures =
shops.stream()
.map(shop -> CompletableFuture.supplyAsync(() -> shop.getName() + " price is " + shop.calculatePrice(product)))
.collect(Collectors.<CompletableFuture<String>>toList());
List<String> prices = priceFutures.stream()
.map(CompletableFuture::join)
.collect(Collectors.<String>toList());
return prices;
//return sequence(priceFutures).join();
}
/*/
public List<String> findPriceSequential(String product) {
return shops
.stream()
.map(shop -> shop.getPrice(product))
.map(Quote::parse)
.map(Discount::applyDiscount)
.collect(Collectors.<String>toList());
}
public List<String> findPriceParallel(String product) {
return shops
.parallelStream()
.map(shop -> shop.getPrice(product))
.map(Quote::parse)
.map(Discount::applyDiscount)
.collect(Collectors.<String>toList());
}
public List<String> findPrice(String product) {
List<CompletableFuture<String>> priceFutures =
findPriceStream(product).collect(Collectors.<CompletableFuture<String>>toList());
return priceFutures.stream().map(CompletableFuture::join).collect(Collectors.<String>toList());
}
public Stream<CompletableFuture<String>> findPriceStream(String product) {
return shops
.stream()
.map(shop -> CompletableFuture.supplyAsync(() -> shop.getPrice(product), executor))
.map(future -> future.thenApply(Quote::parse))
.map(
future ->
future.thenCompose(
quote ->
CompletableFuture.supplyAsync(
() -> Discount.applyDiscount(quote), executor)));
}
public void printPricesStream() {
long start = System.nanoTime();
CompletableFuture[] futures =
findPriceStream("myPhone")
.map(
f ->
f.thenAccept(
s ->
System.out.println(
s
+ " (done in "
+ ((System.nanoTime() - start) / 1_000_000)
+ " msecs)")))
.toArray(size -> new CompletableFuture[size]);
CompletableFuture.allOf(futures).join();
}
}
