What is the working principle of hashmap in Java? The technical analysis Summary of __

One, storage mode:  java HashMap is a key-value pair (key-value) of the form of storage elements.
Second, the calling principle: HashMap requires a hash function that uses the hashcode () and Equals () methods to add and retrieve elements to the collection/from the collection. When the put () method is invoked, HashMap calculates the hash value of the key and then stores the key value pairs on the appropriate index in the collection. If the key already exists, value is updated to the new value.
Third, other heat: Some of the important properties of HashMap are its capacity (capacity), load factor (loading factor) and expansion limit (threshold resizing).