sorting - 合并和排序多个流 java 8

Question

我有多个学生对象流。我必须按排序顺序合并它们。

class Student {
    private String branch;
    private Integer rollNo;
    private Date doj;
    // Getters and Setters
}

在另一个类中，我有一个方法

private Stream<Student> mergeAndSort(Stream<Student> s1, Stream<Student> s2, Stream<Student> s3) {
    return Stream.of(s1, s2, s3).sorted(...
        // I tried this logic multiple times but is not working. How can I inject Student comparator here.
        // I have to sort based on branch and then rollNo.
    );
}

Answer 1

Stream.of(s1, s2, s3)给你一个 Stream<Stream<Student>> .为了得到Stream<Student> , 使用 flatMap :

Stream.of(s1, s2, s3).flatMap(Function.identity()).sorted(...)...

根据需要的属性排序:

return Stream.of(s1, s2, s3)
             .flatMap(Function.identity())
             .sorted(Comparator.comparing(Student::getBranch).thenComparing(Student::getRollNo));