code: public synchronized static void setDefault(ResponseCache responseCache) {
          SecurityManager sm = System.getSecurityManager();
          if (sm != null) {
              // sm.checkPermission(SecurityConstants.SET_RESPONSECACHE_PERMISSION);
          }
          theResponseCache = responseCache;
      }
docs: Sets (or unsets) the system-wide cache.
  
  Note: non-standard procotol handlers may ignore this setting.
  
  @param responseCache The response cache, or
  <code>null</code> to unset the cache.
  
  @throws  SecurityException
  If a security manager has been installed and it denies
  {@link NetPermission}<tt>("setResponseCache")</tt>
  
  @see #getDefault()
  @since 1.5