The GC combinations that were deprecated in JDK 8 have now been removed. This means that the following GC combinations no longer exist:
* DefNew + CMS
* ParNew + SerialOld
* Incremental CMS
The "foreground" mode for CMS has also been removed.

The command line flags that were removed are: `-Xincgc, -XX:+CMSIncrementalMode, -XX:+UseCMSCompactAtFullCollection, -XX:+CMSFullGCsBeforeCompaction` and `-XX:+UseCMSCollectionPassing`.

The command line flag `-XX:+UseParNewGC` no longer has any effect. ParNew can only be used with CMS and CMS requires ParNew. Thus, the `-XX:+UseParNewGC` flag has been deprecated and will likely be removed in a future release.