A package in Java is a way of organizing your classes and interfaces into groups that have a common purpose or theme. They help you avoid naming conflicts, control access to your code, and make it easier to reuse existing code. For example, the java.util package contains classes and interfaces that are useful for working with collections, dates, random numbers, and other utilities. You can use the classes from this package by importing them in your code, such as import java.util.ArrayList;. This allows you to create an object of the ArrayList class, which is a dynamic array that can store any type of data.
You can also create your own packages by using the package keyword at the top of your Java file, followed by the package name. For example, package com.example.myapp;. This declares that your Java file belongs to the com.example.myapp package. You can also create subpackages inside a package by using dots, such as package com.example.myapp.utils;. This creates a subpackage called utils inside the com.example.myapp package. You can then store your classes and interfaces that are related to utilities in this subpackage.
Packages also affect the visibility of your classes and their members. There are four access modifiers in Java: public, protected, default (no modifier), and private. Public classes and members can be accessed from anywhere. Protected classes and members can be accessed from the same package or from subclasses in other packages. Default classes and members can be accessed only from the same package. Private classes and members can be accessed only from the same class.
