System.setProperty("http.proxyHost", "localhost");
System.setProperty("http.proxyPort", "1087");
System.setProperty("https.proxyHost", "localhost");
System.setProperty("https.proxyPort", "1087");

http.proxyHost
http.proxyPort
https.proxyHost
https.proxyPort
http.nonProxyHosts
socksProxyHost
socksProxyPort

java -Dhttp.proxyHost=localhost -Dhttp.proxyPort=1087 -Dhttps.proxyHost=localhost -Dhttps.proxyPort=1087

URL weburl = new URL(URL_STRING);
Proxy webProxy 
  = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("127.0.0.1", 1087));
HttpURLConnection webProxyConnection 
  = (HttpURLConnection) weburl.openConnection(webProxy);