Java collection framework provides you with the complete architecture of objects. Java frameworks group of objects includes – classes, interfaces, and algorithm.

In Java 1.0 and 1.1, the two primary collection classes were Vector and Hashtable, and the Iterator design pattern was implemented in a class called Enumeration.

Collections 101 The Java collections framework is a set of classes and interfaces that implement commonly reusable data collection structures.

In Java, nested classes are categorized as either static member classes or inner classes. Inner classes are non-static member classes, local classes, or anonymous classes.

Sealed classes in Java let developers limit the creation and use of subclasses and preserve the class hierarchy. Here is how sealed classes in Java work.