JAVA

Object is an instance of a class and it is a software unit that combines a structured set of data with a set of operations for inspecting and manipulating that data. When an object is created using new operator, memory is allocated to it.

Interface is similar to a class which may contain method’s signature only but not bodies and it is a formal set of method and constant declarations that must be defined by the class that implements it. Interfaces are useful for:

Methods are functions that operate on instances of classes in which they are defined. Objects can communicate with each other using methods and can call  methods in other classes.

Abstract class is a class designed with implementation gaps for subclasses to fill in and is deliberately incomplete.

Package is a collection of classes and interfaces that provides a high-level layer of access protection and name space management.

An object that implements the Enumeration interface generates a series of elements, one at a time. It has two methods, namely hasMoreElements() and nextElement(). HasMoreElemnts() tests if this enumeration has more elements and nextElement method returns successive elements of the series.