javax.net.debug

 Prints debugging details for connections made.
Example: -Djavax.net.debug=all or -Djavax.net.debug=ssl:handshake:verbose

https.protocols

Controls the protocol version used by Java clients which obtain https connections through use of the HttpsURLConnection class or via URL.openStream() operations. For older versions, this can update the default in case your Java 7 client wants to use TLS 1.2 as its default.
Example: -Dhttps.protocols=TLSv1,TLSv1.1,TLSv1.2

For non-HTTP protocols, this can be controlled through the SocketFactory's SSLContext. 

jdk.tls.client.protocols

Controls the underlying platform TLS implementation . Additional information is available in the JSSE Reference Guide.
Example: -Djdk.tls.client.protocols=TLSv1.1,TLSv1.2
Available in all JDK 8 releases, or after Java 7 update 95 (January 2016) and Java 6 update 121 (July 2016).

http.agent

When initiating connections, Java will apply this as its user-agent string. Modifying this will handle cases where the receiving party responds differently based on the user-agent.
Example: -Dhttp.agent="known agent"

java.net.useSystemProxies

java.net.useSystemProxiesUse proxy details from the operating system itself.
Example: -Djava.net.useSystemProxies=true

http.proxyHost
http.proxyPort

The proxy connection to use for HTTP connections.
Example: -Dhttp.proxyHost=proxy.example.com -Dhttp.proxyPort=8080

https.proxyHost
https.proxyPort

The same as above, except that configuration is separate between HTTP and HTTPS.

http.proxyUser
http.proxyPassword
https.proxyUser
https.proxyPassword

Password-based credentials for the above proxies.