何时以及为何使用 Java 的供应商和消费者接口? [英] When and why would you use Java's Supplier and Consumer interfaces?

问题描述

作为一名学习 Java 的非 Java 程序员，我目前正在阅读有关 Supplier 和 Consumer 接口的内容.我无法理解它们的用法和含义.

As a non-Java programmer learning Java, I am reading about Supplier and Consumer interfaces at the moment. And I can't wrap my head around their usage and meaning.

您何时以及为何使用这些接口?有人可以给我一个简单的外行例子吗?

When and why you would use these interfaces? Can someone give me a simple layperson example of this?

我发现文档示例不够简洁，无法理解.

I'm finding the Doc examples not succinct enough for my understanding.

推荐答案

This is Supplier:

This is Supplier:

public Integer getInteger() {
    return new Random().nextInt();
}

这是消费者:

public void sum(Integer a, Integer b) {
    System.out.println(a + b);
}

因此，通俗地说，供应商是一种返回某些值(如其返回值)的方法.而消费者是一种方法，它消耗一些值(如方法参数)，并对它们进行一些操作.

So in layman terms, a supplier is a method that returns some value (as in its return value). Whereas, a consumer is a method that consumes some value (as in method argument), and does some operations on them.

那些会变成这样的:

// new operator itself is a supplier, of the reference to the newly created object
Supplier<List<String>> listSupplier = ArrayList::new;
Consumer<String> printConsumer = a1 -> System.out.println(a1);
BiConsumer<Integer, Integer> sumConsumer = (a1, a2) -> System.out.println(a1 + a2);

至于用法，非常基本的例子是:Stream#forEach(Consumer) 方法.它需要一个消费者，它消耗您正在迭代的流中的元素，并对每个元素执行一些操作.可能打印出来.

As for usage, the very basic example would be: Stream#forEach(Consumer) method. It takes a Consumer, which consumes the element from the stream you're iterating upon, and performs some action on each of them. Probably print them.

Consumer<String> stringConsumer = (s) -> System.out.println(s.length());
Arrays.asList("ab", "abc", "a", "abcd").stream().forEach(stringConsumer);

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