Java AbstractMap is an abstract class that implements the Java Map interface, providing skeletal implementations for most of the methods in the Map interface. It simplifies the creation of custom map implementations by providing basic functionality like key-value pair insertion and retrieval. Introduced in Java 1997 with Java 1.2, AbstractMap is commonly extended by other Java Map classes, such as Java HashMap and Java TreeMap, to provide specific behaviors for different map types.

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