相关疑难解决方法(0)

我的一位同事向我提出了一个有趣的问题,我无法找到一个整洁而漂亮的Java 8解决方案.问题是流过POJO列表,然后根据多个属性在地图中收集它们 - 映射导致POJO多次出现

想象一下以下POJO:

private static class Customer {
    public String first;
    public String last;

    public Customer(String first, String last) {
        this.first = first;
        this.last = last;
    }

    public String toString() {
        return "Customer(" + first + " " + last + ")";
    }
}

将其设置为List<Customer>:

// The list of customers
List<Customer> customers = Arrays.asList(
        new Customer("Johnny", "Puma"),
        new Customer("Super", "Mac"));

备选方案1:使用Map"流"外部(或更确切地说是外部forEach).

// Alt 1: not pretty since the resulting map is …