More from Java - 1

Packages and API:-

A package in Java is used to group related classes.
Think of it as a folder in a file directory.
We use packages to avoid name conflicts, and to write a better maintainable code.
Packages are divided into two categories:
Built-in Packages (packages from the Java API)
User-defined Packages (create your own packages)

Built-in Packages
The Java API is a library of prewritten classes, that are free to use, included in the Java Development Environment.
The library contains components for managing input, database programming, and much much more.
The library is divided into packages and classes.
Meaning you can either import a single class (along with its methods and attributes), or a whole package that contain all the classes that belong to the specified package.
To use a class or a package from the library, you need to use the import keyword
import package.name.Class; // Import a single class import package.name.*; // Import the whole package

Java Inner Classes:-

In Java, it is also possible to nest classes (a class within a class).
The purpose of nested classes is to group classes that belong together, which makes your code more readable and maintainable.
To access the inner class, create an object of the outer class, and then create an object of the inner class
class OuterClass { int x = 10; class InnerClass { int y = 5; } } public class Main { public static void main(String[] args) { OuterClass myOuter = new OuterClass(); OuterClass.InnerClass myInner = myOuter.new InnerClass(); System.out.println(myInner.y + myOuter.x); } } // Outputs 15 (5 + 10)

One advantage of inner classes, is that they can access attributes and methods of the outer class

Unlike a "regular" class, an inner class can be private or protected.
If you don't want outside objects to access the inner class, declare the class as private

An inner class can also be static, which means that you can access it without creating an object of the outer class