Why does ZonedDateTime now = ZonedDateTime.now(); System.out.println(now.withZoneSameInstant(ZoneOffset.UTC) .equals(now.withZoneSameInstant(ZoneId.of(“UTC”)))); print out false? I would expect the both ZonedDateTime instances to be equal. 1 Answer 1
In Java, is it possible to have a lambda accept multiple different types? I.e: Single variable works: Function <Integer, Integer> adder = i -> i + 1; System.out.println (adder.apply (10)); Varargs also work: Function <Integer [], Integer> multiAdder = ints -> { int sum = 0; for (Integer i : ints) { sum += i; … Read more
I have a problem with the stream of Java 8 foreach attempting to move on next item in loop. I cannot set the command like continue;, only return; works but you will exit from the loop in this case. I need to move on next item in loop. How can I do that? Example(not working): … Read more
This question already has answers here: Is there a concise way to iterate over a stream with indices in Java 8? (23 answers) Closed 8 years ago. Is there a way to build a forEach method in Java 8 that iterates with an index? Ideally I’d like something like this: params.forEach((idx, e) -> query.bind(idx, e)); … Read more
Is it possible to cast a stream in Java 8? Say I have a list of objects, I can do something like this to filter out all the additional objects: Stream.of(objects).filter(c -> c instanceof Client) After this though, if I want to do something with the clients I would need to cast each of them: … Read more
I’m having trouble fully understanding the role that the combiner fulfills in Streams reduce method. For example, the following code doesn’t compile: int length = asList(“str1”, “str2”).stream() .reduce(0, (accumulatedInt, str) -> accumulatedInt + str.length()); Compile error says : (argument mismatch; int cannot be converted to java.lang.String) but this code does compile: int length = asList(“str1”, … Read more
I have a problem trying out the Lambda expressions of Java 8. Usually it works fine, but now I have methods that throw IOException‘s. It’s best if you look at the following code: class Bank{ …. public Set<String> getActiveAccountNumbers() throws IOException { Stream<Account> s = accounts.values().stream(); s = s.filter(a -> a.isActive()); Stream<String> ss = s.map(a … Read more
Javadoc of Collector shows how to collect elements of a stream into a new List. Is there an one-liner that adds the results into an existing ArrayList? 8 Answers 8
In Java 8, there is Stream.collect which allows aggregations on collections. In Kotlin, this does not exist in the same way, other than maybe as a collection of extension functions in the stdlib. But it isn’t clear what the equivalences are for different use cases. For example, at the top of the JavaDoc for Collectors … Read more
General question: What’s the proper way to reverse a stream? Assuming that we don’t know what type of elements that stream consists of, what’s the generic way to reverse any stream? Specific question: IntStream provides range method to generate Integers in specific range IntStream.range(-range, 0), now that I want to reverse it switching range from … Read more