JavaStream去重技巧全解析

List<String> names = Arrays.asList("Alice", "Bob", "Alice", "Charlie", "Bob");
List<String> uniqueNames = names.stream()
                                 .distinct()
                                 .collect(Collectors.toList());
System.out.println(uniqueNames); // 输出: [Alice, Bob, Charlie]

class User {
    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof User)) return false;
        User user = (User) o;
        return age == user.age && Objects.equals(name, user.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }
}

List<User> users = Arrays.asList(
    new User("张三", 25),
    new User("李四", 30),
    new User("张三", 25)
);

List<User> uniqueUsers = users.stream()
                                .distinct()
                                .collect(Collectors.toList());

List<String> uniqueDepartments = users.stream()
                                       .map(User::getDepartment)
                                       .filter(Objects::nonNull)
                                       .distinct()
                                       .collect(Collectors.toList());