When HTTP_2 client try to connect Apache server over HTTPS, the following exception was thrown,
Exception in thread "main" java.io.IOException: Protocol error
at java.net.http.Stream.incoming_reset(java.httpclient@9-internal/Stream.java:356)
at java.net.http.Stream.otherFrame(java.httpclient@9-internal/Stream.java:313)
at java.net.http.Stream.incoming(java.httpclient@9-internal/Stream.java:303)
at java.net.http.Http2Connection.processFrame(java.httpclient@9-internal/Http2Connection.java:458)
at java.net.http.Http2Connection.asyncReceive(java.httpclient@9-internal/Http2Connection.java:388)
at java.net.http.AsyncSSLDelegate.upperRead(java.httpclient@9-internal/AsyncSSLDelegate.java:504)
at sun.net.httpclient.common.Queue.put(java.httpclient@9-internal/Queue.java:82)
at java.net.http.AsyncSSLDelegate.lowerRead(java.httpclient@9-internal/AsyncSSLDelegate.java:454)
at java.net.http.PlainHttpConnection.asyncRead(java.httpclient@9-internal/PlainHttpConnection.java:257)
at java.net.http.PlainHttpConnection$ReadEvent.handle(java.httpclient@9-internal/PlainHttpConnection.java:340)
at java.net.http.HttpClientImpl$SelectorManager.handleEvent(java.httpclient@9-internal/HttpClientImpl.java:373)
at java.net.http.HttpClientImpl$SelectorManager.run(java.httpclient@9-internal/HttpClientImpl.java:343)

But HTTP_1_1 client has no such issue.