JavaDoc and Annotations
JavaDoc and annotations are important tools in Java programming used for documentation and metadata.
JavaDoc
JavaDoc is a tool used to generate documentation for Java classes and methods. It is based on comments and uses specific tags to create documentation so that developers can generate API-like documentation. Here are some commonly used JavaDoc tags:
For Classes or Packages:
@author
: Adds information about the author of the class.@version
: Adds version information to the generated documentation.@since
: Specifies the version when the class or method was created or modified.@see
: Adds a “see also” link to related documents or resources.
For Methods:
@param
: Describes the parameters of a method, including parameter names and descriptions.@return
: Describes the return type and meaning of a method.@throws
or@exception
: Describes the exceptions that a method might throw.@deprecated
: Marks a method as deprecated and usually provides an alternative method.@code
: Displays text in a code font, usually for code examples.
Other Common Tags:
@link
: Provides a link to other resources.@value
: Provides the value for static or member variables.@serial
: Specifies the serial version UID for serialization.
JavaDoc is very useful as it can automatically generate documentation, helping developers and users understand the functionality and usage of the code, classes, and methods. Running the JavaDoc tool can turn comments into documentation.
Example of JavaDoc Comments
1 | /** |
Built-in Annotations
Built-in annotations are annotations provided by Java for metadata and compile-time control. These annotations help the compiler better understand and process the code or serve special purposes. Here are some common usages of built-in annotations:
Applied to Code:
@Override
: Informs the compiler that a method is intended to override a method in the superclass.@Deprecated
: Marks an element (such as a method or class) as deprecated and not recommended for use.@FunctionalInterface
: Indicates that an interface is a functional interface (contains only one abstract method).@SuppressWarnings
: Instructs the compiler to suppress specific types of warnings.@SafeVarargs
: Tells the compiler that a method does not perform unsafe operations on its varargs parameters.
Applied to Other Annotations:
@Retention
: Specifies how long annotations with the annotated type are to be retained (source, class, or runtime).@Documented
: Indicates that the annotated element should be documented by JavaDoc.@Target
: Marks another annotation to restrict where it can be applied (e.g., methods, fields, etc.).@Inherited
: Indicates that an annotation type is automatically inherited.@Repeatable
: Indicates that an annotation type can be repeated.
Example of Using Annotations
1 | // Example of using @Override, @Deprecated, and @SuppressWarnings |
Explanation of Annotations in the Example
@Override
: Indicates thatdisplay
inSubClass
overridesdisplay
inSuperClass
.@Deprecated
: MarksoldMethod
inSuperClass
as deprecated.@SuppressWarnings
: Suppresses warnings about using deprecated methods in theuseOldMethod
method.
Conclusion
JavaDoc and annotations are powerful tools in Java for documenting code and providing metadata that can be used at compile-time or runtime. JavaDoc helps generate comprehensive documentation, making it easier for developers to understand and use the code. Annotations provide a way to add metadata to Java code, enabling advanced features like compile-time checks, runtime processing, and custom behavior implementation through reflection.