java - 通过减少列表上的代码/操作量来优化方法

Question

我想通过将我的操作合并到一个操作中来减少开销，但似乎不太清楚如何在没有错误的情况下完成我的代码

目前我有这个有效的代码:

public Map<String, Invoice> initialize(List<String> paths) {
    List<Invoice> invoices = paths
        .stream()
        .map(Invoice::new)
        .collect(Collectors.toList());

    invoices
        .forEach(e -> {
            e.setInvoiceInputStream(reader(e.getInvoicePath()));
            e.setInvoiceId(invoiceFinder.getInvoiceId(e.getInvoiceInputStream()));
        });

    Map<String, Invoice> invoiceMap = invoices
        .stream()
        .collect(
                Collectors.toMap(
                        e -> e.getInvoiceId(),
                        e -> e)
                );

return invoiceMap;

但是，执行此代码 3 次似乎是浪费时间。如果我尝试不同的东西，比如我收到错误:

return invoicePaths
    .stream()
    .map(Invoice::new)
    .collect(
        Collectors.collectingAndThen(
            Collectors.toList(), list -> {
                list
                    .forEach(e -> {
                        e.setInvoiceInputStream(reader(e.getInvoicePath()));
                        e.setInvoiceId(invoiceFinder.getInvoiceId(e.getInvoiceInputStream()));
});

发票类中的构造函数:

public Invoice(String invoicePath) {
    this.invoicePath = invoicePath;
}

如何通过优化代码来减少开销？

Answer 1

 paths
    .stream()
    .map(Invoice::new)
    .map(e -> {
           e.setInvoiceInputStream(reader(e.getInvoicePath()));
           e.setInvoiceId(invoiceFinder.getInvoiceId(e.getInvoiceInputStream()));
           return e;

    })
    .collect(Collectors.toMap(
                  Invoice::getInvoiceId,
                  Function.identity())
            );

我希望我没有错过任何括号......

想想看，你正在收集到List<Invoice> invoices仅限forEach他们并改变一些东西 - 那不是 Stream::map手术？之后你就是 collect将这些转换为 Map => 之后继续流管道。