#fixed code
                                public static List<Class<?>> getClasses(final String packageName) {
        List<Class<?>> classes = new LinkedList<Class<?>>();

        List<File> paths = getPackageDirectories(packageName);

        for (File path : paths) {
            for (File entry : path.listFiles()) {
                if (isClass(entry.getName())) {
                    Class<?> clazz = getPathEntryAsClass(packageName, entry.getName());
                    classes.add(clazz);
                }
            }
        }

        return classes;
    }
#vulnerable code 
                                public static List<Class<?>> getClasses(final String packageName) {
        List<Class<?>> classes = new LinkedList<Class<?>>();

        File directory = getPackageAsDirectory(packageName);

        for (File entry : directory.listFiles()) {
            if (isClass(entry.getName())) {
                Class<?> clazz = getPathEntryAsClass(packageName, entry.getName());
                classes.add(clazz);
            }
        }

        return classes;
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE