From Java 8 Update 111 (8u111) onwards, the basic authentication scheme has been deactivated, by default, in the Oracle Java Runtime.
If you are using this version (or later), proxies requiring Basic authentication when setting up a tunnel for HTTPS will no longer succeed by default.
Solution
If required, this authentication scheme can be reactivated by removing Basic from the jdk.http.auth.tunneling.disabledSchemes networking property (set at $JAVA_HOME/jre/lib/net.properties), or by setting a system property of the same name to "" ( empty ) in the command line.