Kuidas erinevad HashMap ja Hashtable kogumikud nende rakendamise viiside ja omaduste poolest?

HashMap and Hashtable are implementations of the Map interface in Java, but they have some differences:

• Synchronization: Hashtable is synchronized (thread-safe), which makes it slower in a multithreaded environment. HashMap is not synchronized, so it is faster but not safe for multithreaded access without external synchronization.

• Null allowance: HashMap allows one null key and multiple null values. Hashtable does not allow null keys or null values.

• Inheritance: Hashtable is an older class, inheriting from Dictionary, while HashMap inherits from AbstractMap.

• Usage: In modern applications, it is preferable to use HashMap, and if synchronization is needed, use ConcurrentHashMap or external synchronization of HashMap.

Example of using HashMap:

Map<String, Integer> map = new HashMap<>();
map.put("key", 1);
Integer value = map.get("key");