使用 Lambda 的 Java 8 过滤器数组 [英] Java 8 Filter Array Using Lambda

问题描述

我有一个 double[] 并且我想在一行中过滤掉(创建一个没有新数组)负值而不添加 for 循环.这可以使用 Java 8 lambda 表达式吗?

I have a double[] and I want to filter out (create a new array without) negative values in one line without adding for loops. Is this possible using Java 8 lambda expressions?

在 python 中使用生成器就是这样:

In python it would be this using generators:

[i for i in x if i > 0]

是否可以在 Java 8 中做一些类似的简洁的事情?

Is it possible to do something similarly concise in Java 8?

推荐答案

是的，您可以通过从数组中创建一个 DoubleStream、过滤掉负数并将流转换回一个大批.下面是一个例子:

Yes, you can do this by creating a DoubleStream from the array, filtering out the negatives, and converting the stream back to an array. Here is an example:

double[] d = {8, 7, -6, 5, -4};
d = Arrays.stream(d).filter(x -> x > 0).toArray();
//d => [8, 7, 5]

如果要过滤不是 Object[] 的引用数组，则需要使用 toArray 方法，它采用 IntFunction获取原始类型的数组作为结果:

If you want to filter a reference array that is not an Object[] you will need to use the toArray method which takes an IntFunction to get an array of the original type as the result:

String[] a = { "s", "", "1", "", "" };
a = Arrays.stream(a).filter(s -> !s.isEmpty()).toArray(String[]::new);

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