java stream一些用法_stream java-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_29940863/article/details/125796994

该博客通过一个Java代码示例展示了如何使用Stream API进行数据处理，包括分组、映射、转换和收集操作。主要涉及`groupingBy`、`mapping`、`joining`、`toSet`和`toList`等方法，以及对User对象的属性进行操作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

public static void main(String[] args) {
    List<User> l = Arrays.asList(new User("a", 0), new User("b", 0), new User("c", 1));

    Map<Integer, List<String>> collect = l.stream().collect(Collectors.groupingBy(User::getType, Collectors.mapping(User::getName, Collectors.toList())));
    Map<Integer, Set<String>> collect1 = l.stream().collect(Collectors.groupingBy(User::getType, Collectors.mapping(u -> u.getName() + "qwe", Collectors.toSet())));
    Map<Integer, String> collect2 = l.stream().collect(Collectors.groupingBy(User::getType, Collectors.mapping(User::getName, Collectors.joining(","))));

    List<User> collect3 = l.stream().collect(Collectors.toMap(User::getName, Function.identity(), (c1, c2) -> c1.getType() > c2.getType() ? c1 : c2)).values().stream().sorted(Comparator.comparing(User::getType)).collect(Collectors.toList());

    System.out.println(collect);
    System.out.println(collect1);
    System.out.println(collect2); 
    System.out.println(collect3);
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public static class User {
    private String name;
    private int type;
}

Stream流的使用(保姆级入门教程)_多加点辣也没关系的博客-优快云博客_stream流