Java Annotations

import java.lang.annotation.*;// Simple annotation@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)public @interface LogExecution {}// Annotation with parameters@Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})public @interface Author {    String name();    String date() default "2024-01-01";    String[] tags() default {};}// Marker annotation@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.TYPE)public @interface Serializable {}// Single-value annotation@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.FIELD)public @interface MaxLength {    int value();}// Annotation with enum parameterpublic enum Priority {    LOW, MEDIUM, HIGH}@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.METHOD)public @interface Scheduled {    Priority priority() default Priority.MEDIUM;    int interval() default 60;}// Using annotations@Author(name = "John Doe", tags = {"utility", "helper"})public class UtilityClass {        @LogExecution    @Scheduled(priority = Priority.HIGH, interval = 30)    public void performTask() {        // Method implementation    }        @MaxLength(100)    private String description;}// Annotation processorpublic class AnnotationProcessor {    public static void processAnnotations(Object obj) {        Class<?> clazz = obj.getClass();                if (clazz.isAnnotationPresent(Author.class)) {            Author author = clazz.getAnnotation(Author.class);            System.out.println("Author: " + author.name());        }                for (var method : clazz.getMethods()) {            if (method.isAnnotationPresent(LogExecution.class)) {                System.out.println("Logging execution of: " + method.getName());            }        }    }}

// Built-in annotations@Overridepublic String toString() {    return "Custom toString";}@Deprecatedpublic void oldMethod() {    // Deprecated method}@SuppressWarnings("unchecked")public void suppressWarning() {    // Code with unchecked warnings}@FunctionalInterfaceinterface Calculator {    int calculate(int a, int b);}// Using custom annotations@Author(name = "Alice", date = "2024-01-15", tags = {"api", "v1"})public class ApiService {        @LogExecution    @Scheduled(priority = Priority.HIGH)    public void processData() {        // Method implementation    }        @MaxLength(255)    private String apiKey;}// Processing annotations at runtimeClass<?> clazz = ApiService.class;if (clazz.isAnnotationPresent(Author.class)) {    Author author = clazz.getAnnotation(Author.class);    System.out.println("Author: " + author.name());    System.out.println("Tags: " + Arrays.toString(author.tags()));}// Get method annotationsfor (var method : clazz.getMethods()) {    if (method.isAnnotationPresent(Scheduled.class)) {        Scheduled scheduled = method.getAnnotation(Scheduled.class);        System.out.println("Method " + method.getName() + " priority: " + scheduled.priority());    }}