java - FunctionalInterface Comparator 有 2 个抽象方法

Question

学习 Java 8 Lambda 并想知道编译器如何知道 Comparator 中的哪个方法用于 lambda 表达式？好像不是SAM界面？它有 2 个抽象方法:

@FunctionalInterface
public interface Comparator<T> {
    int compare(T o1, T o2);
    boolean equals(Object obj);
}

Answer 1

equals() 不是抽象方法。此方法覆盖 Object.equals(Object)，并且仅用于 Comparator 接口(interface)能够将 javadoc 附加到该方法，解释比较器应如何实现 equals().

参见 javadoc of FunctionalInterface :

If an interface declares an abstract method overriding one of the public methods of java.lang.Object, that also does not count toward the interface's abstract method count since any implementation of the interface will have an implementation from java.lang.Object or elsewhere.