/**
     * Throws a <code>SecurityException</code> if the
     * calling thread is not allowed to access the package specified by
     * the argument.
     * <p>
     * This method is used by the <code>loadClass</code> method of class
     * loaders.
     * <p>
     * This method first gets a list of
     * restricted packages by obtaining a comma-separated list from
     * a call to
     * <code>java.security.Security.getProperty("package.access")</code>,
     * and checks to see if <code>pkg</code> starts with or equals
     * any of the restricted packages. If it does, then
     * <code>checkPermission</code> gets called with the
     * <code>RuntimePermission("accessClassInPackage."+pkg)</code>
     * permission.
     * <p>
     * If this method is overridden, then
     * <code>super.checkPackageAccess</code> should be called
     * as the first line in the overridden method.
     *
     * @param      pkg   the package name.
     * @exception  SecurityException  if the calling thread does not have
     *             permission to access the specified package.
     * @exception  NullPointerException if the package name argument is
     *             <code>null</code>.
     * @see        java.lang.ClassLoader#loadClass(java.lang.String, boolean)
     *  loadClass
     * @see        java.security.Security#getProperty getProperty
     * @see        #checkPermission(java.security.Permission) checkPermission
     */

    public void checkPackageAccess(String pkg) {

  {- -------------------------------------------
  (1) 
      ---------------------------------------- -}

            if (pkg == null) {
                throw new NullPointerException("package name can't be null");
            }

            String[] pkgs;
            synchronized (packageAccessLock) {
                /*
                 * Do we need to update our property array?
                 */
                if (!packageAccessValid) {
                    String tmpPropertyStr =
                        AccessController.doPrivileged(
                            new PrivilegedAction<String>() {
                                public String run() {
                                    return java.security.Security.getProperty(
                                        "package.access");
                                }
                            }
                        );
                    packageAccess = getPackages(tmpPropertyStr);
                    packageAccessValid = true;
                }

                // Using a snapshot of packageAccess -- don't care if static field
                // changes afterwards; array contents won't change.
                pkgs = packageAccess;
            }

            /*
             * Traverse the list of packages, check for any matches.
             */
            for (int i = 0; i < pkgs.length; i++) {
                if (pkg.startsWith(pkgs[i]) || pkgs[i].equals(pkg + ".")) {
                    checkPermission(
                        new RuntimePermission("accessClassInPackage."+pkg));
                    break;  // No need to continue; only need to check this once
                }
            }
        }