【工具类】常用的工具类——CollectionUtil

苏生Susheng2025-05-24 11:29

目录

cn.hutool.core.collection.CollectionUtil

集合创建

java 复制代码 
List<User> userList = CollectionUtil.list(true);
//true:ArrayList，false：LinkedList

List<String> list1 = Arrays.asList("1", "2", "3", "4", "5");//不可变集合
List<String> list2 = CollectionUtil.toList("1", "2", "3", "4", "5");//可变集合
System.out.println(list2);//[1, 2, 3, 4，5]

集合清空

java 复制代码 
List<String> list = CollectionUtil.toList("1", "2", "3", "4", "5");
CollectionUtil.clear(list);
System.out.println(list);//[]

集合判空

java 复制代码 
List<String> list1 = null;
List<String> list2 = new ArrayList<>();
boolean isEmpty = CollectionUtils.isEmpty(list1); // true
boolean isEmpty = CollectionUtils.isEmpty(list2); // true

List<String> list = Arrays.asList("a", "b", "c");
boolean isNotEmpty = CollectionUtils.isNotEmpty(list); // true

List<String> list1 = null;
List<String> list2 = Arrays.asList("1","2","3");
List<String> result1 = CollectionUtil.emptyIfNull(list1);//[]
List<String> result2 = CollectionUtil.emptyIfNull(list2);//["1","2","3"]

Set<String> set1 = null;
Set<String> set2 = new HashSet<>(Arrays.asList("1","2","3"));
Set<String> result3 = CollectionUtil.emptyIfNull(set1);//[]
Set<String> result4 = CollectionUtil.emptyIfNull(set2);//["1","2","3"]

//空集合给默认值
List<String> list = new ArrayList<>();
List<String> result = CollectionUtil.defaultIfEmpty(list, Arrays.asList("1", "2", "3"));//["1", "2", "3"]

//判断是否有空元素
CollectionUtil.hasNull(list);

集合去重

java 复制代码 
List<String> list = Arrays.asList("a", "b", "a", "c");
List<String> distinctList = CollectionUtil.distinct(list); // ["a", "b", "c"]

集合过滤

java 复制代码 
//List<String> list =Arrays.asList("a", "b", "c");//Arrays.asList()返回的集合是不可变长度的，在这里这么用会报错：UnsupportedOperationException
List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
List<String> filteredList = CollectionUtil.filter(list, e -> e.equals("a")); // ["a"]

集合转换

java 复制代码 
List<String> list = Arrays.asList("1", "2", "3");
List<Integer> mappedList = CollectionUtil.map(list, Integer::valueOf,true); // [1, 2, 3]

集合合并

java 复制代码 
List<String> list1 = Arrays.asList("a", "b");
List<String> list2 = Arrays.asList("b", "c");

Set<String> unionDistinctList = CollectionUtil.unionDistinct(list1, list2); // ["a", "b", "c"]

List<String> unionAllList = (List<String>)CollectionUtil.unionAll(list1, list2); // ["a", "b", "c"]

集合交集

java 复制代码 
List<String> list1 = Arrays.asList("a", "b");
List<String> list2 = Arrays.asList("b", "c");
List<String> intersectionList = (List<String>)CollectionUtil.intersection(list1, list2); // ["b"]

集合差集

java 复制代码 
List<String> list1 = Arrays.asList("a", "b");
List<String> list2 = Arrays.asList("b", "c");
List<String> disjunctionList = (List<String>)CollectionUtil.disjunction(list1, list2); // ["a", "c"]

集合是否包含元素

java 复制代码 
List<String> list = Arrays.asList("a", "b", "c");
boolean contains = CollectionUtil.contains(list, "a"); // true

List<String> list2 = Arrays.asList("a", "b", "c");
List<String> subList = Arrays.asList("a", "b");
boolean containsAll = CollectionUtil.containsAll(list2, subList); // true

集合是否包含指定元素（自定义条件）

java 复制代码 
List<String> list = Arrays.asList("a", "b", "c");
boolean contains = CollectionUtil.contains(list, e -> e.equals("a")); // true

集合分页

java 复制代码 
List<String> list = Arrays.asList("a", "b", "c", "d", "e");
List<String> pageList = CollectionUtil.page(1, 2,list); // ["c", "d"]，页码索引从0开始

集合分组

java 复制代码 
List<User> list = Arrays.asList(
    new User("张三", 18, 1),
    new User("李四", 18, 2),
    new User("王五", 18, 3),
    new User("赵六", 18, 4),
    new User("老七", 18, 1),
    new User("勾八", 18, 1),
    new User("孙九", 18, 3),
    new User("郑十", 18, 2),
    new User("root", 18, 2));
List<List<User>> groupedList = Co
System.out.println(groupedList);
//[[User(name=张三, age=18, grade=1), User(name=老七, age=18, grade=1), User(name=勾八, age=18, grade=1)], 
//[User(name=李四, age=18, grade=2), User(name=郑十, age=18, grade=2), User(name=root, age=18, grade=2)], 
//[User(name=王五, age=18, grade=3), User(name=孙九, age=18, grade=3)], 
//[User(name=赵六, age=18, grade=4)]]

集合转字符串

java 复制代码 
List<String> list = Arrays.asList("a", "b", "c");
String joinedString = CollectionUtil.join(list, ","); // "a,b,c"

元素添加

java 复制代码 
List<String> list = new ArrayList<>(Arrays.asList("1", "2"
CollectionUtil.addAll(list,"4");
CollectionUtil.addAll(list,new String[]{"5","6"});
CollectionUtil.addAll(list,Arrays.asList("7","8"));
CollectionUtil.addAll(list,new HashSet<>(Arrays.asList("9"
System.out.println(list);//[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3"));
CollectionUtil.addAllIfNotContains(list, Arrays.asList("1", "2", "4"));
System.out.println(list);//[1, 2, 3, 4]

List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3"));
CollectionUtil.addIfAbsent(list,"2");//已存在不添加
CollectionUtil.addIfAbsent(list,"4");
System.out.println(list);//[1, 2, 3, 4]

元素删除

java 复制代码 
List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3","","4",null,"5"));
CollectionUtil.removeEmpty(list);
//CollectionUtil.removeBlank(list);
System.out.println(list);//[1, 2, 3, 4，5]

List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3","4","3","5","3","2"));
CollectionUtil.removeAny(list, "3","2");
System.out.println(list);//[1, 4，5]

List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3","","4",null,"5"));
CollectionUtil.removeNull(list);
System.out.println(list);//[1, 2, 3, 4，5]

//自定义条件
List<String> list = new ArrayList<>(Arrays.asList("1", "2", "3","","4",null,"5"));
CollectionUtil.removeWithAddIf(list, item -> item == null || item.isEmpty());
System.out.println(list);//[1, 2, 3, 4，5]

根据属性转Map

java 复制代码 
List<User> list = Arrays.asList(
    new User(1,"张三", 18, 1),
    new User(2,"李四", 18, 2),
    new User(3,"王五", 18, 3),
    new User(4,"张三", 18, 4),
    new User(5,"李四", 18, 1));
Map<String, User> result = CollectionUtil.fieldValueMap(list, "id");

Map<String, User> result2 = CollectionUtil.fieldValueAsMap(list, "id", "name");

获取元素

java 复制代码 
List<User> list = Arrays.asList(
            new User(1,"张三", 18, 1),
            new User(2,"李四", 18, 2),
            new User(3,"王五", 18, 3),
            new User(4,"张三", 18, 4),
            new User(5,"李四", 18, 1));
User result = CollectionUtil.get(list,6);//自带判空效果
User result = CollectionUtil.getFirst(list);
User result = CollectionUtil.getLast(list);
List<User> result = CollectionUtil.getAny(list, 0,  2);
List<Object> result = CollectionUtil.getFieldValues(list, "name");//[张三, 李四, 王五, 张三, 李四]  User类要先实现Iterable<E>接口

//截取集合
List<User> result = CollectionUtil.sub(list, 0, 3);

获取最大/最小元素

java 复制代码 
List<User> list = Arrays.asList(
    new User(1,"张三", 19, 1),
    new User(2,"李四", 18, 2),
    new User(3,"王五", 16, 3),
    new User(4,"张三", 24, 4),
    new User(5,"李四", 17, 1));
//需要User先实现Comparable<e>接口
User result = CollectionUtil.max(list);//张三
User result = CollectionUtil.min(list);//王五

集合排序

java 复制代码 
List<User> list = Arrays.asList(
    new User(1,"张三", 19, 1),
    new User(2,"李四", 18, 2),
    new User(3,"王五", 16, 3),
    new User(4,"张三", 24, 4),
    new User(5,"李四", 17, 1));
//不需要User先实现Comparable<e>接口，默认从小到大排序
List<User> result = CollectionUtil.sort(list, Comparator.comparing(User::getAge));
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