URL url = new URL("jar:file://valid_jar_url_syntax.jar!/")
        URLConnection urlConnection = url.openConnection()
        def original = urlConnection.getDefaultUseCaches()
        urlConnection.setDefaultUseCaches(false)

        try {
            URL[] urls = [new URL("jar:${jar.toURI().toURL()}!/")] as URL[]
            URLClassLoader ucl = new URLClassLoader(urls)
            if (ucl instanceof Closeable) {

            // sun.net.www.protocol.jar.JarURLConnection leaves the JarFile instance open if URLConnection caching is enabled.
            new URL("jar:file://valid_jar_url_syntax.jar!/").openConnection().setDefaultUseCaches(false)
        }
    }

    }

    public boolean getDefaultUseCaches() {
        return connection.getDefaultUseCaches();
    }

    public void setDefaultUseCaches(boolean defaultUseCaches) {
        connection.setDefaultUseCaches(defaultUseCaches);
    }

    public void setRequestProperty(String key, String value) {
        if (key == null) throw new NullPointerException();

    @Override
    public boolean getDefaultUseCaches () {
        return this.connection.getDefaultUseCaches();
    }


    @Override
    public void setDefaultUseCaches ( boolean defaultUseCaches ) {
        this.connection.setDefaultUseCaches(defaultUseCaches);
    }


    @Override
    public int getConnectTimeout () {
        return this.connection.getConnectTimeout();
    }

        try {
            URL url = new URL("jar:file://valid_jar_url_syntax.jar!/");
            URLConnection urlConnection = url.openConnection();
            urlConnection.setDefaultUseCaches(false);
        } catch (IOException e) {
            throw UncheckedException.throwAsUncheckedException(e);
        }
    }

    static Package[] getPackages(ClassLoader classLoader) {