Understanding Runtime annotation checks via reflection

Reflection API allows Java programmer to perform different checks and operations
on class ,fields, methods and annotations during. To make an annotation to be at all visible at runtime,  the RetentionPolicy must be migrated to RUNTIME, as shown in the
below example



@interface MyDefaultAnnotation {


@interface MyRuntimeVisibleAnnotation {


public class AnnotationAtRuntimeTest {

    static class RuntimeCheck1 {

    static class RuntimeCheck2 {

    public static void main(String[] args) {
        Annotation[] annotationsByType = RuntimeCheck1.class.getAnnotations();
        Annotation[] annotationsByType2 = RuntimeCheck2.class.getAnnotations();

        System.out.println("default retention: " + Arrays.toString(annotationsByType));
        System.out.println("runtime retention: " + Arrays.toString(annotationsByType2));

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