Java8--stream流操作对List、List的过滤处理经验分享

应用场景（一）：

    1.对list<map>中map中某个指定的key的value的去重，得到新的list：去除了重复出现指定key的value值得map

示例：

                要求：过滤掉电话相同的map    

List<Map<String, Object>> mapList = new ArrayList<Map<String, Object>>();
Map<String, Object> mapStr1 = new HashMap<String, Object>();
("name", "丽丽");
("sex", "女");
("age", 22);
("tel", "110");
Map<String, Object> mapStr2 = new HashMap<String, Object>();
("name", "丽丽");
("sex", "女");
("age", 23);
("tel", "120");
Map<String, Object> mapStr3 = new HashMap<String, Object>();
("name", "丽丽");
("sex", "女");
("age", 24);
("tel", "110");
(mapStr1);
(mapStr2);

(mapStr3);



ArrayList<Map<String, Object>> cs = ()

.collect(Collectors

.collectingAndThen(Collectors

.toCollection(() -> new TreeSet<>(new Comparator<Map<String, Object>>() {

@Override    //重写比较器
public int compare(Map<String, Object> o1, Map<String, Object> o2) {
if (("tel").equals(("tel"))) {
return 0;
}
return 1;
}

})), ArrayList::new));

               //循环取出结果

(m -> {
("======map========");
().forEach(n -> (n + "-->" + (n)));

});

            

应用场景（二）：

    对list<T>中对象T的指定属性的去重，比如唯一ID，tel，获取新的list:去除了重复出现的指定属性值的对象T

示例：

    要求过滤掉电话相同的user                

User u1 = new User(1, "小米1", "001号", "女", 21, "110");
User u2 = new User(2, "小米2", "002号", "男", 11, "120");
User u3 = new User(3, "小米3", "003号", "女", 21, "119");
User u4 = new User(4, "小米4", "004号", "女", 34, "110");

List<User> persons = (u1, u2, u3, u4);



List<User> unique = ()

                    .collect(Collectors

                    .collectingAndThen(Collectors

                    .toCollection(() -> new TreeSet<>(Comparator

                    .comparing(User::getTel))), ArrayList::new));

                //循环取出结果

(p -> (()));