Lambdas, multiple forEach with casting

Question

Need some help thinking in lambdas from my fellow StackOverflow luminaries.

Standard case of picking through a list of a list of a list to collect some children deep

Answer 1

This would be my version of your code using JDK 8 streams, method references, and lambda expressions:

server.findServices()
    .stream()
    .map(Service::getContainer)
    .filter(Engine.class::isInstance)
    .map(Engine.class::cast)
    .flatMap(engine -> Arrays.stream(engine.findChildren()))
    .filter(Host.class::isInstance)
    .map(Host.class::cast)
    .flatMap(host -> Arrays.stream(host.findChildren()))
    .filter(Context.class::isInstance)
    .map(Context.class::cast)
    .map(context -> {
        ContextInfo info = new ContextInfo(context.getPath());
        info.setThisPart(context.getThisPart());
        info.setNotImportant(context.getNotImportant());
        return info;
    })
    .collect(Collectors.toList());

In this approach, I replace your if-statements for filter predicates. Take into account that an instanceof check can be replaced with a Predicate

Predicate