是否存在注释

//package com.nowjava;

import java.lang.annotation.Annotation;
/* 来自 N o w J a v a . c o m - 时  代  Java*/

public class Main {

    public static void main(String[] argv) throws Exception {

        Class clazz = String.class;

        Class a = String.class;

        System.out.println(isAnnotationPresent(clazz, a));

    }


    public static boolean isAnnotationPresent(Class<?> clazz,

            Class<? extends Annotation> a) {


        if (clazz == null) {

            return false;

        }


        if (clazz.isAnnotationPresent(a)) {/*来自 nowjava - 时代Java*/

            return true;

        }


        if (isAnnotationPresentOnSuperClasses(clazz, a)) {

            return true;

        }


        if (isAnnotationPresentOnInterfaces(clazz, a)) {

            return true;

        }


        return false;

    }


    private static boolean isAnnotationPresentOnSuperClasses(

            Class<?> clazz, Class<? extends Annotation> a) {


        if (clazz == null) {

            return false;

        }


        Class<?> c = clazz.getSuperclass();

        while (c != null && !c.equals(Object.class)) {

            if (c.isAnnotationPresent(a)) {

                return true;

            }

            if (isAnnotationPresentOnInterfaces(c, a)) {

                return true;

            }

            c = c.getSuperclass();

        }


        if (isAnnotationPresentOnInterfaces(clazz.getSuperclass(), a)) {

            return true;

        }


        return false;

    }


    private static boolean isAnnotationPresentOnInterfaces(Class<?> clazz,

            Class<? extends Annotation> a) {


        if (clazz == nul