Stream8.java

// How to loop over nested collections referring to parent elements?
List<Consumer> allConsumersWhoHasHealthDevice = consumerList
        .stream()
        .flatMap(consumer -> consumer.getThings().stream()
                .filter(thing -> thing.isRunning() && Type.HEALTH == thing.getType())
                // This is cool!!!
                .map(thing -> new AbstractMap.SimpleImmutableEntry<>(consumer, thing))
        )
        .map(entry -> entry.getKey())
        .collect(Collectors.toList());
System.out.println(allConsumersWhoHasHealthDevice);
// Output: [Consumer(name=Sri, city=Hyd), Consumer(name=Bob, city=Berlin)]
// In the above code, very interesting point is, we hold the outer/parent element 'Consumer'