#fixed code
                                public static void start(List<GraphvizEngine> engines) throws IOException {
        final String executable = SystemUtils.executableName("java");
        final List<String> cmd = new ArrayList<>(Arrays.asList(
                System.getProperty("java.home") + "/bin/" + executable,
                "-cp", System.getProperty("java.class.path"), GraphvizServer.class.getName()));
        cmd.addAll(engines.stream().map(e -> e.getClass().getName()).collect(toList()));
        new ProcessBuilder(cmd).inheritIO().start();
    }
#vulnerable code 
                                public static void start(List<GraphvizEngine> engines) throws IOException {
        final boolean windows = System.getProperty("os.name").contains("windows");
        final String executable = windows ? "java.exe" : "java";
        final List<String> cmd = new ArrayList<>(Arrays.asList(
                System.getProperty("java.home") + "/bin/" + executable,
                "-cp", System.getProperty("java.class.path"), GraphvizServer.class.getName()));
        cmd.addAll(engines.stream().map(e -> e.getClass().getName()).collect(toList()));
        new ProcessBuilder(cmd).inheritIO().start();
    } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE