使用Java8的Stream对两个 List 遍历匹配数据的优化处理

Question

List<Map<String,Object>> map1 = null; List<Map<String,Object>> map2 = null; for (Map<String, Object> x : map1) { for (Map<String, Object> y : map2) { if (x.get("id").equals(y.get("id"))){ //todo } } } 类似这种用java8的Stream如何操作呢

Answer 1

List<Map<Object, Object>> list1 = new ArrayList<>();
List<Map<Object, Object>> list2 = new ArrayList<>();

list1.stream()
     .filter(map -> list2.stream().anyMatch(map1 -> map.get("id").equals(map1.get("id"))))
     .forEach(map -> {
          // to do sth
     });

你试试这个呢

List<Map<Object, Object>> list3 = list1.stream()
                .map(map -> list2.stream()
                                .filter(m -> Objects.equals(m.get("id"), map.get("id")))
                                .findFirst().map(m -> {
                                    map.putAll(m);
                                    return map;
                                }).orElse(null))
                .filter(Objects::nonNull).collect(Collectors.toList());

Answer 2

是lambda表达式吧？
map1.forEach((k1,v1)->{

map2.forEach((k2,v2)->{
    //todo
})

})