Java AbstractSet.contains() is a method in the Java AbstractSet class that checks whether the specified element is present in the set. It returns true if the element exists in the set, or false if it is not found. Introduced in Java 1997 with Java 1.2, contains() is often used in applications where you need to verify membership in a set, such as checking if a particular item exists in a collection.

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