Question

我需要将Pair<Application, FileObject[]>的流平放到Pair<Application, FileObject>的流。

目前，我已对此进行了编码：

List<Application> applications = this.applicationDao.findAll();
applications.stream()
    .map(app -> 
        new Pair<Application, FileObject[]>(
            app,
            this.massiveInterfaceService.getPendingDocuments(app)
        )
    );

因此，我需要获取Pair<app, FileObject>的信息流。

this.massiveInterfaceService.getPendingDocuments是：

public Stream<FileObject> getPendingDocuments(Application app) { /*...*/ }

有什么想法吗？

Answer 1

假设massiveInterfaceService.getPendingDocuments()返回FileObject[]，则可以创建如下方法：

Stream<Pair<Application, FileObject>> flatten(Pair<Application, FileObject[]> pair) {
   return Arrays.stream(pair.getRight())
                .map(fileObject -> new Pair.of(pair.getLeft(), fileObject));
}

然后在您的信息流中使用它：

Stream<Pair<Application, FileObject>> stream =
   applications.stream()
        .map(app -> 
            Pair.of(app, this.massiveInterfaceService.getPendingDocuments(app)))
        .flatMap(this::flatten);

另一方面，如果massiveInterfaceService.getPendingDocuments()返回Stream<FileObject>

Stream<Pair<Application, FileObject>> stream =
   applications.stream()
        .flatMap(app -> 
            this.massiveInterfaceService
                .getPendingDocuments(app)))
                .map(fileObject -> Pair.of(app, fileObject)));

从您的问题尚不清楚哪个是正确的。

Answer 2

您可以简单地调用flatMap，从getPendingDocuments的结果创建流。这是因为getPendingDocuments已经返回了流。

applications.stream()
   .flatMap(app -> this.massiveInterfaceService
                    .getPendingDocuments(app)
                    .map(doc -> Pair.of(app, doc));

Java流：从Pair <k，object [] =“”>到Pair <k，object =“”>

2 个答案: