summary

Hashtable is also implemented based on hash table, which is similar to map, but hashtable is thread safe, and hashtable does not allow null key or value

Member variable

Like HashMap, the data structure of hashtable is implemented by array and linked list

Several member variables are the same as HashMap:

method

The hashtable method is basically the same as HashMap, except that the hashtable method adds the synchronized keyword to ensure that the hashtable is thread safe

Mainly talk about the differences between hashtable and HashMap:

There is a static method in the collections class: synchronizedmap (), which creates a thread safe map object and returns it as an encapsulated object.