Java 中的箭头运算符“->"有什么作用? [英] What does the arrow operator, '->', do in Java?

问题描述

在搜索一些代码时，我遇到了箭头运算符，它到底是做什么的?我以为 Java 没有箭头运算符.

While hunting through some code I came across the arrow operator, what exactly does it do? I thought Java did not have an arrow operator.

return (Collection<Car>) CollectionUtils.select(listOfCars, (arg0) -> {
        return Car.SEDAN == ((Car)arg0).getStyle();
});

详细信息:Java 6、Apache Commons Collection、IntelliJ 12

Details: Java 6, Apache Commons Collection, IntelliJ 12

更新/答案:事实证明，IntelliJ 12 支持 Java 8，它支持 lambda，并且正在折叠"谓词并将它们显示为 lambda.下面是展开"的代码.

Update/Answer: It turns out that IntelliJ 12 supports Java 8, which supports lambdas, and is "folding" Predicates and displaying them as lambdas. Below is the "un-folded" code.

return (Collection<Car>) CollectionUtils.select(listOfCars, new Predicate() {
    public boolean evaluate(Object arg0) {
        return Car.SEDAN == ((Car)arg0).getStyle();
    }
});

推荐答案

这是新的 lambda 表达式语法的一部分，将在 Java 8 中引入.有几个在线教程可以掌握它，这里是一个链接到一个.基本上，-> 将参数(左侧)与实现(右侧)分开.

That's part of the syntax of the new lambda expressions, to be introduced in Java 8. There are a couple of online tutorials to get the hang of it, here's a link to one. Basically, the -> separates the parameters (left-side) from the implementation (right side).

使用 lambda 表达式的一般语法是

The general syntax for using lambda expressions is

(参数)->{ Body } 其中 -> 分隔参数和 lambda 表达式主体.

(Parameters) -> { Body } where the -> separates parameters and lambda expression body.

参数用括号括起来，这与方法相同，而且 lambda 表达式主体是用大括号括起来的代码块.

The parameters are enclosed in parentheses which is the same way as for methods and the lambda expression body is a block of code enclosed in braces.

这篇关于Java 中的箭头运算符“->"有什么作用?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IT屋！