How do I create custom annotations in Java?

How do I create custom annotations in Java?

To create a custom annotation in Java, you use the @interface keyword. Here's a simple example:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyCustomAnnotation {
    String value();
}

This defines an annotation that can be applied to methods.

What do the @Retention and @Target annotations do?

The @Retention annotation specifies how long the annotation is retained. For example, RUNTIME means it's available at runtime. The @Target annotation specifies where the annotation can be applied, like methods, fields, or classes.

Can I add parameters to my custom annotation?

Yes, you can add parameters to your custom annotation. For example, you can define it like this:

public @interface MyCustomAnnotation {
    String value();
    int count() default 1;
}

This allows you to specify a value and an optional count.

How do I use my custom annotation in code?

You can use your custom annotation by applying it to a method like this:

@MyCustomAnnotation(value="Hello", count=5)
public void myMethod() {
    // method implementation
}

Then, you can access the annotation using reflection.