为什么“Lambda表达式中使用的变量必须是最终的或有效的最终”？警告忽略实例变量

问题描述

我正在研究java 8流，我唯一的问题是理解lambdas是为什么lambdas中的有效最终警告被忽略的实例（和静态）变量。我似乎无法在网上找到任何参考，因为大多数网页只会谈论有效最终的定义。

I'm studying java 8 streams and the only problem I have is understanding lambdas is why the effectively final warning in lambdas is ignored for instance(and static) variables. I can't seem to find any reference to it online, as most pages will just talk about the definition of being "effectively final".

public class LambdaTest {

    int instanceCounter = 0;

    public void method() {
        int localCounter = 0;
        instanceCounter = 5; //Re-assign instance counter so it is no longer effectively final

        Stream.of(1,2,3).forEach(elem -> instanceCounter++); //WHY DOES THE COMPILER NOT COMPLAIN HERE
        Stream.of(1,2,3).forEach(elem -> localCounter++); //Does not compile because localCounter is not effectively final
    }
}

推荐答案

我们倾向于忘记 instanceCounter 实际上是 this.instanceCounter ，你是捕获这个哪个好，有效最终。至于为什么这是需要的，答案显然是

We tend to forget that instanceCounter is actually this.instanceCounter, you are capturing this which is well, effectively final. As to why this is needed, the answer is obviously here

这篇关于为什么“Lambda表达式中使用的变量必须是最终的或有效的最终”？警告忽略实例变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！