#vulnerable code 
                                private Map<String, LoaderServiceInfo> discoverServices(File libDir,
            Map<String, LoaderServiceInfo> existingPackages) {
        logFine("Checking for updates in " + libDir.toURI());
        Map<String, LoaderServiceInfo> discoveredPackages = new HashMap<String, LoaderService.LoaderServiceInfo>();

        boolean updated = false;
        for (File file : libDir.listFiles()) {
            if (!file.getName().endsWith(".jar")) {
                continue;
            }
            logFine("Found jar file %s", file.toURI());

            LoaderServiceInfo packageInfo = existingPackages.get(file.toURI().toString());
            if (packageInfo != null) {
                long lastModified = file.lastModified();
                if (lastModified == packageInfo.fileUpdateTimeMillis) {
                    // Jar file has been previously loaded.
                    // Add to the list of discovered packages and skip.
                    discoveredPackages.put(file.toURI().toString(), packageInfo);
                    continue;
                }
            }

            try (JarInputStream jar =
                    new JarInputStream(new FileInputStream(file))) {
                while (true) {
                    JarEntry e = jar.getNextJarEntry();
                    if (e == null) {
                        break;
                    }

                    String name = e.getName();

                    // Assuming specific naming convention for
                    // Service classes
                    if (isValidServiceClassName(name)) {
                        logFine("Found service class %s", name);
                        String className =
                                name.replaceAll(".class", "").replaceAll("/", ".");

                        if (packageInfo == null) {
                            packageInfo = new LoaderServiceInfo();
                        }

                        packageInfo.name = file.getName();
                        packageInfo.fileUpdateTimeMillis = file.lastModified();
                        updated |= (null == packageInfo.serviceClasses.put(className, null));

                        discoveredPackages.put(file.toURI().toString(), packageInfo);
                    }
                }
            } catch (IOException e) {
                logWarning("Problem loading package %s, Exception %s",
                        file.getName(), Utils.toString(e));
            }
        }

        if (updated) {
            return discoveredPackages;
        }

        return null;
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private Map<String, LoaderServiceInfo> discoverServices(File libDir,
            Map<String, LoaderServiceInfo> existingPackages) {
        logFine("Checking for updates in " + libDir.toURI());
        Map<String, LoaderServiceInfo> discoveredPackages = new HashMap<String, LoaderService.LoaderServiceInfo>();

        boolean updated = false;
        File[] files = libDir.listFiles();
        if (files == null) {
            return null;
        }
        for (File file : files) {
            if (!file.getName().endsWith(".jar")) {
                continue;
            }
            logFine("Found jar file %s", file.toURI());

            LoaderServiceInfo packageInfo = existingPackages.get(file.toURI().toString());
            if (packageInfo != null) {
                long lastModified = file.lastModified();
                if (lastModified == packageInfo.fileUpdateTimeMillis) {
                    // Jar file has been previously loaded.
                    // Add to the list of discovered packages and skip.
                    discoveredPackages.put(file.toURI().toString(), packageInfo);
                    continue;
                }
            }

            try (JarInputStream jar =
                    new JarInputStream(new FileInputStream(file))) {
                while (true) {
                    JarEntry e = jar.getNextJarEntry();
                    if (e == null) {
                        break;
                    }

                    String name = e.getName();

                    // Assuming specific naming convention for
                    // Service classes
                    if (isValidServiceClassName(name)) {
                        logFine("Found service class %s", name);
                        String className =
                                name.replaceAll(".class", "").replaceAll("/", ".");

                        if (packageInfo == null) {
                            packageInfo = new LoaderServiceInfo();
                        }

                        packageInfo.name = file.getName();
                        packageInfo.fileUpdateTimeMillis = file.lastModified();
                        updated |= (null == packageInfo.serviceClasses.put(className, null));

                        discoveredPackages.put(file.toURI().toString(), packageInfo);
                    }
                }
            } catch (IOException e) {
                logWarning("Problem loading package %s, Exception %s",
                        file.getName(), Utils.toString(e));
            }
        }

        if (updated) {
            return discoveredPackages;
        }

        return null;
    }