Do you want to add information about the code as meta data? If your answer is yes then this is the feature to add annotations.
Why is it needed?
It is used to provide supplementary information about the classes, member variables and functions.
What is the difference between annotations and comments?
Annotations provides the meta data about coding which can be
used by tools and compilers. But comments are simple information to know about
coding.
Syntax:
‘@’ annotation name
Annotation types:
Annotations can be classified into the following types..
1. Built- in annotations:
These are annotations created by the java itself
Eg: ‘@Depreccated’, ’@Override’, ‘@SuppressWarnings’
2. Custom annotations:
The user can create this type of annotations.
Eg:
‘@interface’
Java code for built-in annotation:
These are included in java package itself. Here ‘@Override’
is used.
This annotation is used to tell the compiler that this base
class code is overridden.
Base class or Super class: sClass1
Child class: cClass
Method: display() – same method with two definition is
called overridden.
Sample Code:
class sClass1 {
void display()
{
System.out.println("This is the Super Class");
}
}
class cClass
extends sClass1 {
@Override
void display()
{
System.out.println("This is the Child Class");
}
}
Next type of annotation is given below.
Java code for custom annotation:
User
defined annotations are called custom annotation. Here, the custom annotations
are listed below..
@Retention :it specifies how long the annotations are
retained.
@Target : It specifies the kind of program, the annotations
are applicable.
@interface : user defined interface
@custAnnotation: user defined custom annotation name.
Sample Code:
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface custAnnotation {
String name();
}
public class egClass {
@custAnnotation("This
is the custom annotation")
public void egMethod()
{
// Method
implementation
}
}
These are the sample codes used to provide annotations in
both built-in and custom type. Hope this codes are useful to you.Keep coding!!!
