Long time to build from a ics file

Describe the bug I try to read a quite large ics file (1.4Mb, 2400 events) and it takes nearly one minute

To Reproduce Steps to reproduce the behavior: I use the java library, version 3.0.6, with this code :

    URL icsUrl = new URL(url);
    HttpURLConnection connexion = (HttpURLConnection)icsUrl.openConnection();

    try (InputStream flux = connexion.getInputStream())
    {  
        CalendarBuilder builder = new CalendarBuilder();
        Calendar calendar = builder.build(flux);
    }

The builder.build(flux) takes nearly 1 minute (I tried to download directly the ics file and it takes less than 1sec)

Is there any way to read it faster ?

[alfonsobonso]

Trying to get closer to this, I am testing with a ics file from my local file system - ~800k, 2500 events with a similar vanilla config as above. It seems the changes in 3.0.5 have severely impacted performance. Average times (ms) to run the builder.build(inputStream):

version time 3.0.9 86477 3.0.6 89591 3.0.5 90608 3.0.4 501 3.0.1 484

It spends a lot of time in:

at java.util.Collections$SynchronizedMap.get(Collections.java:2584) - waiting to lock <0x000000008b642ba8> (a java.util.Collections$SynchronizedMap) at net.fortuna.ical4j.model.DateTime$DateFormatCache.get(DateTime.java:544)

and much time in the construction of java.util.(GregorianCalendar), but I haven’t been able to get closer comparing the 3.0.4 and 3.0.5 release code changes

[vonox7]

Thanks @benfortuna! 3.0.18 fixes now this issue, both CPU and GC levels are back to the state as it was with version 3.0.4! Thank you for the fast fix!