从中间结果初始化变量

Question

有时，当源代码变得复杂时，我会发现读下面这样的语句会让人困惑：

Set<Integer> odds = new HashSet<>(ints); // not yet true
odds.removeAll(evens); // now it's true

(Set<Integer> odds = new HashSet<>(ints)).removeAll(evens); // doesn't compile

Set<Integer> odds = new HashSet<Integer>(ints) {{ removeAll(evens); }};

Set<Integer> odds = (odds = new HashSet<>(ints)).retainAll(evens) ? odds : odds

Set<Integer> odds;
(odds = new HashSet<Integer>(ints)).removeAll(evens);

Answer 1

使用流：

Set<Integer> odds =
    ints.stream().filter(x -> x % 2 == 1).collect(Collectors.toSet());

如果您想同时将集合划分为赔率和均分：

Map<Boolean, Set<Integer>> oddsAndEvens =
    ints.stream().collect(
        Collectors.partitioningBy(x -> x % 2 == 0, Collectors.toSet()));
Set<Integer> evens = oddsAndEvens.get(true);
Set<Integer> odds = oddsAndEvens.get(false);