Java - exact meaning http.maxConnections
Code inspection shows that the property is only used to limit the size of the keep-alive cache - so unless I'm mistaken that's really the maximum number of idle connections.
Implementation libraries use it as ambiguously as the standards language.
for example, apache http components, arguably the most used HTTP client in java, uses it for literal maximum number of concurrent connections to a single host: https://hc.apache.org/httpcomponents-client-ga/httpclient/xref/org/apache/http/impl/client/HttpClientBuilder.html#L1005