IDEA告警：Can be replaced with ‘.values().stream()‘

背景

• IDEA 又搞黄色了！

详解

可替换为.values().stream()。 检查信息：通知可以简化的流API调用链。它可以避免遍历集合时创建多余的临时对象。 此检查替换了以下调用链：

collection.stream().forEach() → collection.forEach() collection.stream().collect(toList/toSet/toCollection()) → new CollectionType<>(collection) collection.stream().toArray() → collection.toArray() Arrays.asList().stream() → Arrays.stream() or Stream.of() IntStream.range(0, array.length).mapToObj(idx -> array[idx]) → Arrays.stream(array) IntStream.range(0, list.size()).mapToObj(idx -> list.get(idx)) → list.stream() Collections.singleton().stream() → Stream.of() Collections.emptyList().stream() → Stream.empty() stream.filter().findFirst().isPresent() → stream.anyMatch() stream.collect(counting()) → stream.count() stream.collect(maxBy()) → stream.max() stream.collect(mapping()) → stream.map().collect() stream.collect(reducing()) → stream.reduce() stream.collect(summingInt()) → stream.mapToInt().sum() stream.mapToObj(x -> x) → stream.boxed() stream.map(x -> {...; return x;}) → stream.peek(x -> ...) !stream.anyMatch() → stream.noneMatch() !stream.anyMatch(x -> !(...)) → stream.allMatch() stream.map().anyMatch(Boolean::booleanValue) -> stream.anyMatch() IntStream.range(expr1, expr2).mapToObj(x -> array[x]) -> Arrays.stream(array, expr1, expr2) Collection.nCopies(count, ...) -> Stream.generate().limit(count) stream.sorted(comparator).findFirst() -> Stream.min(comparator) 

替换语义在某些情况下可能会有细微的差别。例如

• 当Collections.synchronizedList(...).forEach()同步时，Collections.synchronizedList(...).stream().forEach()不同步
• collect(Collectors.maxBy())将返回空的Optional，如果结果元素为null，而Stream.max()在这种情况下将抛NullPointerException