stream流分组归类

使用Stream流对数据进行分组归类可以通过Stream的collect方法结合Collectors.groupingBy方法来实现。groupingBy方法接受一个Function作为参数，用于指定根据哪个属性进行分组。下面是一个示例代码：

List<String> list = Arrays.asList("apple", "banana", "cherry", "date", "elderberry");

Map<Integer, List<String>> groupedMap = list.stream()
        .collect(Collectors.groupingBy(String::length));

System.out.println(groupedMap);

以上代码将根据字符串的长度进行分组，输出的结果为：

{5=[apple], 6=[banana, cherry], 4=[date], 9=[elderberry]}

其中，键是字符串的长度，值是对应长度的字符串列表。可以看到，长度为5的字符串有一个，长度为6的字符串有两个，长度为4和9的字符串各有一个。

这样就实现了对Stream流中的元素进行分组归类。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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