问题描述
最近我开始探索Java 8，我无法理解Java功能实现lambda表达式所必需的功能接口的概念。有一个来介绍Java中的lambda函数，但是我被困在。定义如下：
Recently I started exploring Java 8 and I can't quite understand the concept of "functional interface" that is essential to Java's implementation of lambda expressions. There is a pretty comprehensive guide to lambda functions in Java, but I got stuck on the chapter that gives definition to the concept of functional interfaces. The definition reads:
然后他进入示例，其中一个是 Comparator interface：
An then he proceeds to examples, one of which is Comparator interface:
public interface Comparator<T> {
int compare(T o1, T o2);
boolean equals(Object obj);
}
我能够测试我可以使用lambda函数代替Comparator参数，它可以工作（即 Collections.sort（list，（a，b） - > ab））。
I was able to test that I can use a lambda function in place of Comparator argument and it works(i.e. Collections.sort(list, (a, b) -> a-b)).
但是在Comparator界面中，比较和等于方法是抽象的，这意味着它有两个抽象方法。那么，如果定义要求接口具有恰好一个抽象方法，那么它如何起作用呢？我在这里缺少什么？
But in the Comparator interface both compare and equals methods are abstract, which means it has two abstract methods. So how can this be working, if the definition requires an interface to have exactly one abstract method? What am I missing here?
推荐答案
来自：
我真的不能说它更好。
修改：根据Maurice的评论更新至本页最新文本（谢谢！）
Updated to the most recent text of this page, per Maurice's comment (thanks!)
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