Creating a Map from a Set and a Function Here are two classes that should each do the job. The first just shows a map view of the set, while the second can write values back to the set through a special interface. Call Syntax: Map<K,V> immutable = new SetBackedMap<K,V>(Set<K> keys, Function<K,V> func); Map<K,V> mutable … Read more
In java 11 there is a new method Predicate::not. So you can filter out empty string : list.stream() .filter(Objects::nonNull) .filter(Predicate.not(String::isEmpty))
@Vivin’s answer is correct, but I think it’s useful to explain why Guava doesn’t have any method to allow you to transform the keys of a Map (or to transform a Set at all). All of Guava’s methods for transforming and filtering produce lazy results… the function/predicate is only applied when needed as the object … Read more
Probably the most efficient way is ImmutableSet.copyOf(list).asList(), which eliminates duplicates and preserves iteration order. (But your implementation with LinkedHashSet would be nearly as efficient, and wouldn’t throw up on nulls, in the unlikely event you actually wanted nulls in your collection.)
Update: This has been added to Guava as Futures.withTimeout(). Internally, we have a makeTimeoutFuture method that takes a Future as input and returns a new Future that will have the same result unless the original hasn’t completed by a given deadline. If the deadline expires, the output Future has its result set to a TimeoutException. … Read more
Assuming you have class Entity { final long id; final String data; public long getId() { return id; } public String getData() { return data; } Entity(long id, String data) { this.id = id; this.data = data; } } In Java 8 you can write Collection<Entity> entities = Arrays.asList(new Entity(1, “one”), new Entity(11, “eleven”), new … Read more
Your implementation is wrong 😉 Basically docs says (I’ll paraphrase and emphasise): @throws NullPointerException if input is null and the concrete function implementation does not accept null arguments By implementing your function you must decide if it accepts nulls or not. In first case: private static final class Example implements Function<MyBean, String> { @Override @Nullable … Read more
You can use @SuppressWarnings(“UnstableApiUsage”) to suppress those warnings.
Why doesn’t the enhanced for loop just accept an iterator? I want to gather a few of the potential reasons from the various answers as to why the for-each loop doesn’t simply accept an iterator. Convenience: The for-each loop was created partly for convenience for the common operation of performing an action given each element … Read more
You can use the standard Collections#min() for this. Map<String, Double> map = new HashMap<String, Double>(); map.put(“1.1”, 1.1); map.put(“0.1”, 0.1); map.put(“2.1”, 2.1); Double min = Collections.min(map.values()); System.out.println(min); // 0.1 Update: since you need the key as well, well, I don’t see ways in Collections or Google Collections2 API since a Map is not a Collection. The … Read more