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💡Definition

– Group of similar types of classes, interfaces and subpackages.

💡Categories-

Comparing built-in and user-defined packages in Java:

Feature	Built-in Packages	User-defined Packages
Provided by	Java runtime environment	Developer
Contains	Pre-defined classes, interfaces, and methods	Classes and interfaces defined by developer
Importing	Automatically imported	Must be explicitly imported using import keyword
Naming convention	Follows specific convention (e.g. java.util, java.io)	Can be named by developer, as long as it is a valid Java identifier
Purpose	Provide pre-defined functionality	Organize and reuse developer’s own code

💡1- Built in packages

– also called as predefined packages in java
 i.e- java.lang, java.util, java.io etc

💡2- User defined packages

-also called as developer/user defined packages

[To use class of other package, we have 3 options to choose]

Option	Syntax	Example
Fully Qualified Name	package.ClassName.methodName()	java.util.ArrayList.add()
Import using Package.Class before Class Declaration	import Package.Class;	import java.util.ArrayList;
Import Full Package	import Package.*;	import java.util.*;
Static Import	import static Package.Class.methodName;	import static java.lang.Math.PI;

💡a- using fully qualified name

💡b- by importing package.class (recommended)

💡C- by importing full package*

Note– importing package doesn’t include subpackage

💡Static Import–

used to import only static member of a class instead of class.

Interview Questions —

• How packages are related to access modifiers?
• How many ways are available to import class of other packages?