code: public void activate(InetAddress host, int port, Collection<String> nonProxyHosts) {
          for (String scheme : new String[] {"http", "https"}) {
              String currentProxyHost = System.getProperty(scheme + ".proxyHost");
              String currentProxyPort = System.getProperty(scheme + ".proxyPort");
              if (currentProxyHost != null) {
                  originalProxies.put(scheme, new InetSocketAddress(currentProxyHost, Integer.parseInt(currentProxyPort)));
              }
              System.setProperty(scheme + ".proxyHost", new InetSocketAddress(host, port).getHostString());
              System.setProperty(scheme + ".proxyPort", Integer.toString(port));
          }
  
          String currentNonProxyHosts = System.getProperty("http.nonProxyHosts");
          if (currentNonProxyHosts == null) {
              originalNonProxyHosts.clear();
          } else {
              for (String nonProxyHost : Splitter.on('|').split(currentNonProxyHosts)) {
                  originalNonProxyHosts.add(nonProxyHost);
              }
          }
          System.setProperty("http.nonProxyHosts", Joiner.on('|').join(nonProxyHosts));
      }
docs: Activates a proxy override for the given URI scheme.