Basic Runtime Annotation

Annotations.java

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

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation {
   String name() default "";
}

class Annotated {
   @MyAnnotation(name = "Mary")
   public void hello(String name) {
      System.out.println("Hello " + name + "!");
   }
}

class AnnotationRunner {
   public void run(Class<?> klass) throws Exception {
      for (Method method : klass.getMethods()) {
         if (method.isAnnotationPresent(MyAnnotation.class)) {
            MyAnnotation myAnnotation = method.getAnnotation(MyAnnotation.class);
            String name = myAnnotation.name();
            method.invoke(klass.newInstance(), name);
         }
      }
   }
}

public class Annotations {
   public static void main(String[] args) throws Exception {
      AnnotationRunner runner = new AnnotationRunner();
      runner.run(Annotated.class);
   }
}