Annotations

Annotations in Java provide metadata about the program. This tutorial will teach you how to use annotations.

Built-in Annotations

Java provides several built-in annotations:

  • @Override – Indicates that a method is intended to override a method in a superclass.
  • @Deprecated – Indicates that a method is deprecated and should not be used.
  • @SuppressWarnings – Suppresses specific compiler warnings.

Creating Custom Annotations

You can create your own custom annotations by using the @interface keyword:


import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation {
    String value();
}

public class Main {
    @MyAnnotation(value = "Hello, World!")
    public void myMethod() {
        System.out.println("This is my method.");
    }
    
    public static void main(String[] args) {
        Main main = new Main();
        main.myMethod();
    }
}

Using Annotations with Reflection

You can use reflection to access annotation information at runtime:


import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;

@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation {
    String value();
}

public class Main {
    @MyAnnotation(value = "Hello, World!")
    public void myMethod() {
        System.out.println("This is my method.");
    }
    
    public static void main(String[] args) throws Exception {
        Main main = new Main();
        Method method = main.getClass().getMethod("myMethod");
        MyAnnotation annotation = method.getAnnotation(MyAnnotation.class);
        System.out.println("Annotation value: " + annotation.value());
    }
}

Continue exploring our intermediate tutorials to learn more about Java programming.

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