<applet code="MyApplet.class" width="300" height="200">
 <param name="policyfile" value="mypolicy.policy">
</applet>

Policy policy = Policy.getInstance("JavaPolicy", new URIParameter(new File("mypolicy.policy").toURI()));
AccessController.doPrivileged(new PrivilegedAction() {
  public Object run() {
    // 在这里编写需要特定权限的代码
    return null;
  }
}, policy.getPermissions());