Java 8流 - 对象的总和 [英] Java 8 stream - sum of objects

问题描述

假设我有一个在接口下面实现的对象列表：

Let's say I have a list of objects implementing below interface:

public interface Summable<T> {
    T add(T o1);
}

假设我还有一些能够对这些对象求和的类： / p>

Let's say I have also some class which is able to sum these objects:

public class Calculator<T extends Summable<T>> {
    public T sum(final List<T> objects) {
        if (null == objects) {
            throw new IllegalArgumentException("Ups, list of objects cannot be null!");
        }
        T resultObject = null;
        for (T object : objects) {
            resultObject = object.add(resultObject);
        }
        return resultObject;
   }
}

如何使用Java 8流实现相同目标？

How can I achieve the same using Java 8 streams?

我正在玩一个自定义收集器，但无法弄清楚一些简洁的解决方案。

I'm playing around a custom Collector, but couldn't figure out some neat solution.

推荐答案

你所拥有的是减少：

return objects.stream().reduce(T::add).orElse(null);

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