1. Create and Use a Simple Custom Annotation
This program demonstrates how to create a simple custom annotation. The annotation is applied to a method and accessed using reflection.
import java.lang.annotation.*;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface MyAnnotation {
String message();
}
class Demo {
@MyAnnotation(message = "Welcome to Java Annotations")
public void display() {
System.out.println("Display Method Executed");
}
}
public class SimpleAnnotationExample {
public static void main(String[] args) throws Exception {
Demo obj = new Demo();
obj.display();
Method method = Demo.class.getMethod("display");
MyAnnotation annotation = method.getAnnotation(MyAnnotation.class);
System.out.println("Annotation Message: " + annotation.message());
}
}Output:
Display Method Executed
Annotation Message: Welcome to Java Annotations2. Student Information Using Custom Annotation
This program demonstrates a custom annotation with multiple elements. The annotation stores student information and retrieves it using reflection.
import java.lang.annotation.*;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface StudentInfo {
int id();
String name();
}
class Student {
@StudentInfo(id = 101, name = "Rahul")
public void details() {
System.out.println("Student Details");
}
}
public class StudentAnnotationExample {
public static void main(String[] args) throws Exception {
Student obj = new Student();
obj.details();
Method method = Student.class.getMethod("details");
StudentInfo info = method.getAnnotation(StudentInfo.class);
System.out.println("Student ID : " + info.id());
System.out.println("Student Name : " + info.name());
}
}Output:
Student Details
Student ID : 101
Student Name : Rahul3. Author Information Using Custom Annotation
This program creates a custom annotation to store author details. The annotation values are accessed at runtime using reflection.
import java.lang.annotation.*;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface Author {
String name();
String version();
}
class Book {
@Author(name = "Raja", version = "1.0")
public void showBook() {
System.out.println("Java Programming Book");
}
}
public class AuthorAnnotationExample {
public static void main(String[] args) throws Exception {
Book obj = new Book();
obj.showBook();
Method method = Book.class.getMethod("showBook");
Author author = method.getAnnotation(Author.class);
System.out.println("Author : " + author.name());
System.out.println("Version : " + author.version());
}
}Output:
Java Programming Book
Author : Raja
Version : 1.0Code language: CSS (css)4. Employee Details Using Custom Annotation
This program demonstrates the use of a custom annotation for employee details. The annotation values are displayed using Java Reflection API.
import java.lang.annotation.*;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface EmployeeInfo {
int id();
String department();
}
class Employee {
@EmployeeInfo(id = 201, department = "Software")
public void employeeDetails() {
System.out.println("Employee Information");
}
}
public class EmployeeAnnotationExample {
public static void main(String[] args) throws Exception {
Employee obj = new Employee();
obj.employeeDetails();
Method method = Employee.class.getMethod("employeeDetails");
EmployeeInfo info = method.getAnnotation(EmployeeInfo.class);
System.out.println("Employee ID : " + info.id());
System.out.println("Department : " + info.department());
}
}Output:
Employee Information
Employee ID : 201
Department : Software5. Course Details Using Custom Annotation
This program creates a custom annotation to store course details. The annotation information is retrieved and displayed at runtime.
import java.lang.annotation.*;
import java.lang.reflect.Method;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface Course {
String courseName();
int duration();
}
class Training {
@Course(courseName = "Java Programming", duration = 45)
public void courseDetails() {
System.out.println("Course Information");
}
}
public class CourseAnnotationExample {
public static void main(String[] args) throws Exception {
Training obj = new Training();
obj.courseDetails();
Method method = Training.class.getMethod("courseDetails");
Course course = method.getAnnotation(Course.class);
System.out.println("Course Name : " + course.courseName());
System.out.println("Duration : " + course.duration() + " Days");
}
}Output:
Course Information
Course Name : Java Programming
Duration : 45 Days