_.group

public static <T, K> Map<K, List<T>> group(Stream<T> dataStream, Function<? super T, ? extends K> keyApply)

public static <T, K, V> Map<K, List<V>> group(Stream<T> dataStream, Function<? super T, ? extends K> keyApply,

Function<? super T, ? extends V> valueApply)

参数

• dataSources (List<T>) 待参加计算的数据信息。
• keyApply 分组项,作为map的key
• valueApply 数据转换器,作为map的value

返回值

• Map<K, List<V> 返回一个Map类型分组结果

例子

List<Person> peoples = Arrays.asList(

new Person(12, "孙悟空"),

new Person(12, "猪八戒"),

new Person(12, "孙悟空")

);

Map<String, List<Person>> group = EnhanceStream.group(peoples, Person::getName);

Console.log(group);

//=>{孙悟空=[Person{age=12, name='孙悟空'}, Person{age=12, name='孙悟空'}], 猪八戒=[Person{age=12, name='猪八戒'}]}

Map<String, List<String>> nameList = EnhanceStream.group(peoples, Person::getName,Person::getName);

Console.log(nameList);

//=>{孙悟空=[孙悟空, 孙悟空], 猪八戒=[猪八戒]}