Note: Ms. Watson was unaware of the properties of the watch, and could not recall precisely how she acquired it, saying only that it was a gift from a former coworker. When questioned about the person in question, she was not able to provide details. Item Description:Metal sign, white ...
Map Map 是一个接口,它是 Java 集合框架的一部分。 它定义了存储键值对(key-value pairs)的通用操作,如添加、删除和检索元素等。 Map 接口不能直接实例化,因为它是一个抽象类型。 HashMap HashMap 是Map 接口的一个具体实现类。 它基于哈希表的数据结构来存储键值对。 HashMap 允许使用 null 值和null 键。