JDK 21.0.2 Release Notes

The java.net.ExtendedSocketOptions TCP_KEEPIDLE and TCP_KEEPINTERVAL are supported on Windows platforms starting from Windows 10 version 1709 and onwards. TCP_KEEPCOUNT is supported starting from Windows 10 version 1703 and onwards.

The JDK 21 issue that could potentially lead to JVM crashes or incorrect execution when running the JVM with -XX:+UseZGC and non-default value of -XX:ObjectAlignmentInBytes has been resolved, and it is possible again to use this combination of JVM options.

Apple’s final release of the 14.4 update to macOS 14 Sonoma causes some Java applications on Apple silicon systems (M1/M2/M3) to terminate unexpectedly. The issue is not present on Intel-based systems and affects all Java versions.

Although most Java applications will not be affected, at this time there is no practical way to determine if they will be. There is currently no workaround.

A section containing the thread local lock stack has been added to hs_err report files. It only gets printed when the new lightweight locking mode is enabled (-XX:LockingMode=2).

An example is given here with details about the locked objects omitted:

Lock stack of current Java thread (top to bottom):
LockStack[1]: nsk.share.jdi.EventHandler 
...
LockStack[0]: java.util.Collections$SynchronizedRandomAccessList
...

It lists objects which are lightweight locked, through synchronized methods or statements, by the Java thread which is being analyzed. The object which has been locked most recently is printed first. Objects which are not lightweight locked are not displayed in this section.

On Linux, if the JVM is started with +UseTransparentHugePages but the system does not support Transparent Huge Pages, a warning will now be printed to stdout:

UseTransparentHugePages disabled; transparent huge pages are not supported by the operating system.

NMT reports will now show peak values for all categories. Peak values contain the highest value for committed memory in a given NMT category over the lifetime of the JVM process.

If the committed memory for an NMT category is currently at peak, NMT prints "at peak"; otherwise, it prints the peak value.

For example:

-                  Compiler (reserved=230KB, committed=230KB)
                            (malloc=34KB #64) (peak=49KB #71) 
                            (arena=196KB #4) (peak=6126KB #16)

This shows Compiler arena memory peaked at a bit more than 6MB, whereas it now hovers around 200 KB.

The following root certificates have been added to the cacerts truststore:

+ eMudhra Technologies Limited
  + emsignrootcag1
    DN: CN=emSign Root CA - G1, O=eMudhra Technologies Limited, OU=emSign PKI, C=IN

+ eMudhra Technologies Limited
  + emsigneccrootcag3
    DN: CN=emSign ECC Root CA - G3, O=eMudhra Technologies Limited, OU=emSign PKI, C=IN

+ eMudhra Technologies Limited
  + emsignrootcag2
    DN: CN=emSign Root CA - G2, O=eMudhra Technologies Limited, OU=emSign PKI, C=IN

The following root certificates have been added to the cacerts truststore:

+ DigiCert, Inc.
  + digicertcseccrootg5
    DN: CN=DigiCert CS ECC P384 Root G5, O="DigiCert, Inc.", C=US

+ DigiCert, Inc.
  + digicertcsrsarootg5
    DN: CN=DigiCert CS RSA4096 Root G5, O="DigiCert, Inc.", C=US

+ DigiCert, Inc.
  + digicerttlseccrootg5
    DN: CN=DigiCert TLS ECC P384 Root G5, O="DigiCert, Inc.", C=US

+ DigiCert, Inc.
  + digicerttlsrsarootg5
    DN: CN=DigiCert TLS RSA4096 Root G5, O="DigiCert, Inc.", C=US

The following root certificate has been added to the cacerts truststore:

+ Let's Encrypt
  + letsencryptisrgx2
    DN: CN=ISRG Root X2, O=Internet Security Research Group, C=US

The following root certificate has been added to the cacerts truststore:

+ Telia Root CA v2
  + teliarootcav2
    DN: CN=Telia Root CA v2, O=Telia Finland Oyj, C=FI