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– Group of similar types of classes, interfaces and subpackages.
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 |
|Naming convention||Follows specific convention (e.g. ||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]
|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;|
💡C- by importing full package*
Note– importing package doesn’t include subpackage
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?