As to http.maxConnections, the document says as follows.

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http.maxConnections (default: 5)
    If HTTP keep-alive is enabled, this value is the number of idle connections that will be simultaneously kept alive, per-destination.

( http://download.oracle.com/javase/6/docs/technotes/guides/net/properties.html)
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The followings are the source code portion where the above-mentioned is implemented.

-------j2se/src/share/classes/sun/net/www/http/KeepAliveCache.java (jdk6u23)----
...

249 /* return a still valid, unused HttpClient */
250 synchronized void put(HttpClient h) {
251 if (size() > KeepAliveCache.getMaxConnections()) {
252 h.closeServer(); // otherwise the connection remains in limbo
253 } else {
254 push(new KeepAliveEntry(h, System.currentTimeMillis()));
255 }
256 }
...
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At the line#251, the compare condition is "greater than".
This seems that the program can cache(keep alive) the number of http.maxConnections+1.