Java HashMap.put() is a method in the Java HashMap class used to insert a key-value pair into the map. If the key already exists in the map, it updates the value associated with that key. This method is one of the most commonly used for adding entries to a map in Java, and is essential for working with associative data structures. Introduced in Java 1995 with Java 1.2, put() is part of Java's Java Collections Framework and allows for efficient key-value management.

https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html