多个流筛选器或forEach if-else

Question

null

List<String> sublist1 = list.stream().filter(condition1).collect(ImmutableList.toImmutableList());
List<String> sublist2 = list.stream().filter(condition2).collect(ImmutableList.toImmutableList());

List<String> sublist1 = new LinkedList<>();
List<String> sublist2 = new LinkedList<>();
list.stream().forEach(element -> {
    if(condition1) sublist1.add(element);
    else if (condition2) sublist2.add(element);
})

Answer 1

如果特定有两个条件导致两个子列表，并且它们是可选的，即两个条件中只有一个可能为true，则可以在filter或predicate.OR中使用或，然后根据任一条件使用Collectors.PartitioningBy：

java prettyprint-override">Map<Boolean, List<String>> sublistMap = list
        .stream()
        .filter(condition1.or(condition2))
        .collect(Collectors.partitioningBy(condition1, Collectors.toUnmodifiableList()));

List<String> sublist1 = sublistMap.get(Boolean.TRUE); // condition1
List<String> sublist2 = sublistMap.get(Boolean.FALSE); // condition2

测试

List<String> list = Arrays.asList("a", "b", "cc", "ddd", "aaaa", "vvv", "oo");
Predicate<String> condition1 = (s) -> s.contains("o");
Predicate<String> condition2 = (s) -> s.contains("a");

System.out.println(sublist1);
System.out.println(sublist2);

输出：

[oo]
[a, aaaa]