public static void main(String[] args) {
// how many sales?
long saleCount = saleStream().count();
System.out.println("Count of sales: " + saleCount);
// any sales over $100?
Supplier<DoubleStream> totalStream = () -> saleStream().mapToDouble(Sale::total);
boolean bigSaleDay = totalStream.get().anyMatch(total -> total > 100.00);
System.out.println("Big sale day? " + bigSaleDay);
// maximum sale amount?
DoubleSummaryStatistics stats = totalStream.get().summaryStatistics();
System.out.println("Max sale amount: " + stats.getMax());
System.out.println("Stats on total: " + stats);
// how many items were sold today?
Supplier<Stream<Item>> itemStream = () -> saleStream().flatMap(sale -> sale.items.stream());
long itemCount = itemStream.get().count();
System.out.println("Count of items: " + itemCount);
// which different items were sold today?
String uniqueItems =
itemStream.get().map(item -> item.identity).distinct().collect(Collectors.joining(" & "));
System.out.println("Distinct items: " + uniqueItems);
// summarize sales by store
ConcurrentMap<String, DoubleSummaryStatistics> summary =
saleStream()
.parallel()
.collect(
Collectors.groupingByConcurrent(
sale -> Thread.currentThread().getName(),
Collectors.summarizingDouble(Sale::total)));
System.out.println("Summary by thread: " + summary);
summary
.keySet()
.stream()
.sorted()
.forEach(store -> System.out.println(store + " stats: " + summary.get(store)));
}
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setDaemon(true);
return t;
}