Java Proxy Verification - Output current proxy in use for a supplied URL (if any) with no dependencies outside JavaSE

WhatIsMyProxy.java

import java.net.Proxy;
import java.net.ProxySelector;
import java.net.URI;

public class WhatIsMyProxy
{
    public static void main(String[] args)
    {
        String website = args[0];
        Proxy proxy = ProxySelector.getDefault().select(URI.create(website)).iterator().next();
        System.out.format("proxy.address=%s%nproxy.type.name=%s%n", proxy.address(), proxy.type().name());
    }
}

Compiling:

javac WhatIsMyProxy.java

Running with no proxy:

$ java WhatIsMyProxy https://example.com/
proxy.address=null
proxy.type.name=DIRECT

Running with system proxies:

> java -Djava.net.useSystemProxies=true WhatIsMyProxy https://example.com/
proxy.address=localhost:3128
proxy.type.name=HTTP

Running with an explicit HTTP proxy:

> java -Dhttps.proxyHost=localhost -Dhttps.proxyPort=3128 WhatIsMyProxy https://example.com/
proxy.address=localhost:3128
proxy.type.name=HTTP

Running with an explicit SOCKS proxy:

> java -DsocksProxyHost=localhost -DsocksProxyPort=3128 WhatIsMyProxy https://example.com/
proxy.address=localhost:3128
proxy.type.name=SOCKS

Read more Proxies - Networking Properties on Oracle's documentation site.