A package in Java is a rule used to group your related classes, interfaces and sub-packages.
A Java package organizes Java classes into namespaces, providing a unique namespace .
packages provides a good structure of the project incase huge amount of classes and files.
There are two types of package
- Built-in Packages
- User-defined Packages
User-defined Packages
package that is defined by the programmer. Classes and interfaces can be added to a package by including the package
statement at the beginning of the source file, followed by the package name.
To create a package in Java, use the package
keyword in package declaration.
package [PACKAGE_NAME];
class [CLASS_NAME]{
public static void main(String[] args) {
System.out.println("This is my first package!");
}
Built-in Packages
JDK is best example of built-in packages.
To use Built-in Packages from the library, you need to use the import
keyword
Import the whole package with .*
import package.name.*;
Import the specific class from package
import package.name.Class;
Example of most popular built-in package
java.sql
java.lang
java.util
java.net
java.io
java.awt
features:
- Preventing naming conflicts.
- Security
- data encapsulation (or data-hiding)
- Code reusability