Java Annotation

//没有参数的annotation定义
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotationNoValue {
}

//有参数的annotation定义
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotationMultiValue {
    String hello() default "I‘m the default value";
    int number() default 0;
    int [] arrays() default {1,2,3};
}

//annotation测试代码
public class AnnotationTest {

    @MyAnnotationNoValue
    public void annotationNoValue(){

    }
    @MyAnnotationSingleValue("the single value")
    public void annotationSingleValue(){

    }
    @MyAnnotationMultiValue(hello="I‘m joy, hello", number = 123, arrays = {6,6,6})
    public void annotationMultiValue(){

    }

    public static void main(String args[]) throws Exception{
        AnnotationTest test = new AnnotationTest();

        Method method = AnnotationTest.class.getMethod("annotationNoValue", null);
        if(method.isAnnotationPresent(MyAnnotationNoValue.class)){
            System.out.println("no value annotation" + method.getAnnotation(MyAnnotationNoValue.class));
        }

        method = AnnotationTest.class.getMethod("annotationSingleValue", null);
        if(method.isAnnotationPresent(MyAnnotationSingleValue.class)){
            System.out.println("one value annotation" + method.getAnnotation(MyAnnotationSingleValue.class).value());
        }

        method = AnnotationTest.class.getMethod("annotationMultiValue", null);
        if(method.isAnnotationPresent(MyAnnotationMultiValue.class)){
            System.out.println("one value annotation" + method.getAnnotation(MyAnnotationMultiValue.class).hello());
            System.out.println("one value annotation" + method.getAnnotation(MyAnnotationMultiValue.class).number());
            System.out.println("one value annotation" + method.getAnnotation(MyAnnotationMultiValue.class).arrays().toString());
        }
    }
}