A DESCRIPTION OF THE PROBLEM :
https://github.com/openjdk/jdk/blob/9d764ee48ee7c2e7be7a25aee2ed7bed2fcd2000/src/java.base/share/classes/sun/net/www/http/KeepAliveCache.java#L131-L140

shows that this is in the current source and not only in JDK 1.8

public synchronized void remove (HttpClient h, Object obj) {
    // [...]
    if (v != null) {
        v.remove(h);
        if (v.empty()) {
            removeVector(key);
        }
    }
}

v is of type ClientVector which extends Stack<KeepAliveEntry> while h is of type HttpClient.
ClientVector has thus two remove methods:
 - remove(Object) which will not do the right thing, so that remove implementation never will have any effect on the entries of the stack.
 - remove(HttpClient) which does the right thing and will remove the HttpClient.

Although the code is correct this is not immediately obvious and it might help to rename the overloaded method to help with code readibility.