Java的8个流和操作上的阵列 [英] Java 8 Stream and operation on arrays

问题描述

我刚刚发现了新的Java 8个流能力。在Python来了，我在想，如果现在有一个整洁的方式做像总结阵列作业，在一行Python化的方式相乘两个数组？

I have just discovered the new Java 8 stream capabilities. Coming from Python, I was wondering if there was now a neat way to do operations on arrays like summing, multiplying two arrays in a "one line pythonic" way ?

感谢

推荐答案

有加入 java.util.Arrays中的新的方法，以一个数组转换成一个Java 8个流然后可以用于求和等

There are new methods added to java.util.Arrays to convert an array into a Java 8 stream which can then be used for summing etc.

int sum =  Arrays.stream(myIntArray)
                 .sum();

乘两个数组是有点困难，因为我不能想办法来获取值，并在同一时间作为流操作的指数。这意味着你可能要流在阵列的索引。

Multiplying two arrays is a little more difficult because I can't think of a way to get the value AND the index at the same time as a Stream operation. This means you probably have to stream over the indexes of the array.

//in this example a[] and b[] are same length
int[] a = ...
int[] b = ...

int[] result = new int[a.length];

IntStream.range(0, a.length)
        .forEach( i-> result[i] = a[i]* b[i]);

修改
  霍尔格评论者指出，可以使用地图方法，而不是的forEach 是这样的：

EDIT Commenter Holger points out you can use the map method instead of forEach like this:

int[] result = IntStream.range(0, a.length).map( i->a[i]* b[i]).toArray();

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