#vulnerable code 
                                public Randomizer<?> getRandomizer(Field field) {
        Class<?> fieldType = field.getType();
        Pattern patternAnnotation = getAnnotation(field, Pattern.class);

        final String regex = patternAnnotation.regexp();
        if (fieldType.equals(String.class)) {
            return new RegularExpressionRandomizer(regex, random.nextLong());
        }
        return null;
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public Randomizer<?> getRandomizer(Field field) {
        Class<?> fieldType = field.getType();
        Pattern patternAnnotation = io.github.benas.randombeans.util.ReflectionUtils
                .getAnnotation(field, Pattern.class);

        final String regex = patternAnnotation.regexp();
        if (fieldType.equals(String.class)) {
            return new RegularExpressionRandomizer(regex, random.nextLong());
        }
        return null;
    }