In Java, a package is a way to organize related classes and interfaces into a single namespace. It provides a mechanism for grouping related classes and helps in avoiding naming conflicts. A package consists of a collection of classes, interfaces, sub-packages, and other resources.
Packages are declared using the package keyword at the beginning of a Java source file. The package declaration should be the first non-comment line in the file. For example:
Packages are organized in a hierarchical structure, similar to directories in a file system. The naming convention for packages follows the reverse domain name convention, where the package name starts with the top-level domain name in reverse order, followed by subsequent components. For example, com.example.myapp is a common convention for package names.
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Packages provide several benefits
- Encapsulation: Packages help in organizing classes and encapsulating them within a common namespace. They provide a level of access control, allowing classes within the same package to access each other’s package-private (default) members.
- Code Reusability: By grouping related classes together, packages facilitate code reusability. Other developers can use the classes in a package by importing the package and accessing the public classes/interfaces within it.
- Namespace Management: Packages help in avoiding naming conflicts. Different packages can have classes with the same name without any conflict because the fully qualified name of a class includes the package name.
To use classes from another package in your Java code, you need to import them using the import statement. For example
how to import java packages
This allows you to use the MyClass class from the com.example.myapp package in your code.
Note that Java provides some predefined packages, such as java.lang, which is automatically imported into every Java source file, and packages from the Java Standard Library, such as java.util and java.io, which contain commonly used classes and utilities.