RELEASE NOTES: JDK 16

JEP 390: Warnings for Value-based Classes

Users of the value-based classes provided by the standard libraries—notably including users of the primitive wrapper classes—should avoid relying on the identity of class instances. Programmers are strongly discouraged from calling the wrapper class constructors, which are now deprecated for removal. New javac warnings discourage synchronization on value-based class instances. Runtime warnings about synchronization can also be activated, using command-line option -XX:DiagnoseSyncOnValueBasedClasses.

For further details, see JEP 390.

C-Style Array Declarations Are Not Allowed in Record Components

Prior to JDK 16, the javac compiler accepted C-style array declarations in record components. The JLS 16 now forbids it. In particular, the compiler had accepted code such as:

` record R(int i[]) {} `

This code is no longer acceptable according to the specification for JDK 16. Section 8.10.1 of the JLS 16 defines the syntax of a record component as:

` RecordComponent: {RecordComponentModifier} UnannType Identifier VariableArityRecordComponent VariableArityRecordComponent: {RecordComponentModifier} UnannType { Annotation } ... Identifier RecordComponentModifier: Annotation ` which clearly forbids C-style array declarations in record components. To fix this issue, the compiler has been synchronized with the JLS 16, so that C-style array declarations are no longer allowed in record components.

Annotation Interfaces May Not Be Declared As Local Interfaces

Prior to JDK 16, the javac compiler accepted annotations declared as local interfaces. Now the JLS 16 at section 14.3 forbids it. For example, the javac compiler had accepted code such as:

` class C { void m() { @interface A {} } } `

This code is no longer acceptable according to Section [14.3] of the JLS 16: "A local interface may be a normal interface (§9.1), but not an annotation interface (§9.6)."

To fix this issue, the javac compiler implementation has been synchronized with the JLS 16, so that annotation interfaces cannot be declared as local interfaces.

DocLint Support Moved to jdk.javadoc Module

The code that provides the DocLint feature in javac has been moved from the jdk.compiler module to the jdk.javadoc module. For most users, there will be no impact. However, any user wanting to build a minimal image for running javac with DocLint enabled will need to ensure that the jdk.javadoc module is available when linking the image.

Argument Index of Zero or Unrepresentable by int Throws IllegalFormatException.

Format string specifiers now throw exceptions when given values outside of valid ranges of values.

The Formatter class in java.util defines format specifiers such as argument indexes, argument widths, and argument precisions. Numeric values that are invalid (zero for argument index) or too large (beyond the size of an int) could create unexpected results with undefined behavior. This update gives explicit value ranges for these format specifiers. Widths and indexes will be valid from [1, Integer.MAXVALUE] and precision fields will be valid from [0, Integer.MAXVALUE]. Values outside of these ranges will result in IllegalFormatException or one of its subclasses being thrown. Note that argument indexes of zero prior to this change did not throw an exception and produced behavior that was undefined, but had the appearance of correctness despite causing side effects that were not obvious.

`HttpPrincipal::getName` Returned Incorrect Name

The behavior of the HttpPrincipal::getName method has been updated to return the name in the correct format as outlined in its specification, i.e. "realm:username". Previously, the method incorrectly returned "username" only.

The Default HttpClient Implementation Returns Cancelable Futures

In this release, the default HttpClient returns cancelable futures.

The default HttpClient is created by a call to HttpClient.newHttpClient(), or by invoking the build method on builders returned by HttpClient.newBuilder(). The implementation of the sendAsync methods in the default HttpClient now return CompletableFuture objects that are cancelable. Invoking cancel(true) on a cancelable future that is not completed, attempts to cancel the HTTP exchange in an effort to release underlying resources as soon as possible. More information can be obtained by reading the API documentation of the HttpClient::sendAsync methods.

HttpClient.newHttpClient and HttpClient.Builder.build Might Throw UncheckedIOException

Creation of an instance of java.net.http.HttpClient may fail with UncheckedIOException if the underlying resources required by the implementation cannot be allocated.

Typically, this may happen if the underlying resources required to opening a java.nio.channels.Selector are not available. In this case Selector.open() will throw an IOException which the default implementation of java.net.http.HttpClient will wrap in an UncheckedIOException. The API documentation of HttpClient.newHttpClient() and HttpClient.newBuilder().build() have been updated to specify that UncheckedIOException may be thrown if the underlying resources required by the implementation cannot be allocated. Prior to this change, an undocumented InternalError would have been thrown.

Make JVMTI Table Concurrent

For improved performance, JVM/TI ObjectFree events are no longer posted within GC pauses. The events are still posted as requested, and will be posted before ObjectFree events are enabled or disabled with SetNotificationMode. SetNotificationMode can be used to explicitly flush ObjectFree events, if needed.

Support for CLDR Version 38

Locale data based on Unicode Consortium's CLDR has been upgraded to their version 38. For the detailed locale data changes, please refer to the Unicode Consortium's CLDR release notes: - http://cldr.unicode.org/index/downloads/cldr-38

Support Supplementary Characters in String Case Insensitive Operations

Case insensitive operations in java.lang.String class now correctly do case insensitive comparisons for supplementary characters (characters which have code point values over U+FFFF). For details, see the updates to the methods: ` - compareToIgnoreCase(String other) - equalsIgnoreCase(String other) - regionMatches(boolean ignoreCase, ...) For example, `` "\ud801\udc00".equalsIgnoreCase("\ud801\udc28") `` returnstrue`, because '𐐀' ("\ud801\udc00") and '𐐨' ("\ud801\udc28") are equal to each other character in case insensitive comparison.

Terminally Deprecated ThreadGroup stop, destroy, isDestroyed, setDaemon and isDaemon

The stop, destroy, isDestroyed, setDaemon and isDaemon methods defined by java.lang.ThreadGroup have been terminally deprecated in this release.

ThreadGroup::stop is inherently unsafe and has been deprecated since Java 1.2. The method is now terminally deprecated and will be removed in a future release.

The API and mechanism for destroying a ThreadGroup is inherently flawed. The methods that support explicitly or automatically destroying a thread group have been terminally deprecated and will be removed in a future release.

SunPKCS11 Provider Supports SHA-3 Related Algorithms

The SunPKCS11 provider has been updated with SHA-3 algorithm support. Additional KeyGenerator support for Hmac using message digests other than SHA-3 has also been added. When the corresponding PKCS11 mechanisms are supported by the underlying PKCS11 library, the SunPKCS11 provider now supports the following additional algorithms:

• MessageDigest: SHA3-224, SHA3-256, SHA3-384, SHA3-512
• Mac: HmacSHA3-224, HmacSHA3-256, HmacSHA3-384, HmacSHA3-512
• Signature: SHA3-224withDSA, SHA3-256withDSA, SHA3-384withDSA, SHA3-512withDSA, SHA3-224withDSAinP1363Format, SHA3-256withDSAinP1363Format, SHA3-384withDSAinP1363Format, SHA3-512withDSAinP1363Format, SHA3-224withECDSA, SHA3-256withECDSA, SHA3-384withECDSA, SHA3-512withECDSA, SHA3-224withECDSAinP1363Format, SHA3-256withECDSAinP1363Format, SHA3-384withECDSAinP1363Format, SHA3-512withECDSAinP1363Format, SHA3-224withRSA, SHA3-256withRSA, SHA3-384withRSA, SHA3-512withRSA, SHA3-224withRSASSA-PSS, SHA3-256withRSASSA-PSS, SHA3-384withRSASSA-PSS, SHA3-512withRSASSA-PSS.
• KeyGenerator: HmacMD5, HmacSHA1, HmacSHA224, HmacSHA256, HmacSHA384, HmacSHA512, HmacSHA512/224, HmacSHA512/256, HmacSHA3-224, HmacSHA3-256, HmacSHA3-384, HmacSHA3-512.

JEP 397: Sealed Classes (Second Preview)

Sealed classes and interfaces have been previewed again in JDK 16, initially added to the Java language in JDK 15. Sealed classes and interfaces restrict which other classes or interfaces may extend or implement them.

For further details, see JEP 397.

JEP 395: Records

Records have been added to the Java language. Records are a new kind of class in the Java language. They act as transparent carriers for immutable data with less ceremony than normal classes.

Since nested classes were first introduced to Java, with the exception of static final fields initialized by constant expressions, nested class declarations that are inner have been prohibited from declaring static members. This restriction applies to non-static member classes, local classes, and anonymous classes.

JEP 384: Records (Second Preview) added support for local interfaces, enum classes, and record classes, all of which are static definitions. This was a well-received enhancement, permitting coding styles that reduce the scope of certain declarations to local contexts.

While JEP 384 allowed for static local classes and interfaces, it did not relax the restriction on static member classes and interfaces of inner classes. An inner class could declare a static interface inside one of its method bodies, but not as a class member.

As a natural next step, JEP 395 further relaxes nesting restrictions, and permits static classes, methods, fields, etc., to be declared within inner classes.

For further details, see JEP 395.

JEP 394: Pattern Matching for instanceof

Pattern matching for the instanceof operator has been made a final and permanent feature of the Java language in JDK 16. Pattern matching allows common logic in a Java program to be expressed more concisely and safely, namely the conditional extraction of components from objects.

For further details, see JEP 394.

JEP 387: Elastic Metaspace

JEP 387 "Elastic Metaspace" overhauls the VM-internal metaspace- and class-space-implementation. Less memory is used for class metadata. The savings effect is mostly noticeable in scenarios involving lots of small grained class loaders. Upon class unloading, memory is timely returned to the operating system.

A switch is added to fine-tune metaspace reclamation: -XX:MetaspaceReclaimPolicy=(balanced|aggressive|none). balanced, the default, causes the VM to reclaim memory while keeping computational overhead minimal; aggressive moderately increases the reclaim rate at the cost of somewhat more expensive bookkeeping; none switches reclamation off altogether.

The switches InitialBootClassLoaderMetaspaceSize and UseLargePagesInMetaspace have been deprecated.

Object Monitors No Longer Keep Strong References to Their Associated Object

When synchronization is performed on an object, an association is established between the object and the object monitor that implements the synchronization. In the past, the reference from a monitor to its associated object was a strong reference. These strong references would be observable through JVM TI functions that walk the heap (reported as JVMTI_HEAP_ROOT_MONITOR or JVMTI_HEAP_REFERENCE_MONITOR) and in heap dumps (reported as HPROF_GC_ROOT_MONITOR_USED). As of this release, a weak reference is used. These are not observable to JVM TI or heap dumps. Consequently, JVMTI_HEAP_ROOT_MONITOR, JVMTI_HEAP_REFERENCE_MONITOR and HPROF_GC_ROOT_MONITOR_USED are longer reported.

Add Process-Memory Information to `hs-err` and `VM.info`

On Linux, process memory information has been added to both JVM crash reports (hs_err files) and the VM.info diagnostic jcmd. This information contains the process' virtual size, its resident set size, and how much memory was swapped out. If the JVM uses glibc, the size of glibc outstanding allocations and retained memory are printed, as well as the (glibc tunables)[https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html].

Deprecated Tracing Flags Are Obsolete and Must Be Replaced With Unified Logging Equivalents

When Unified Logging was added in Java 9, a number of tracing flags were deprecated and mapped to their unified logging equivalent. These flags are now obsolete and will no longer be converted automatically to enable unified logging. To continue getting the same logging output, you must explicitly replace the use of these flags with their unified logging equivalent.

| Obsoleted Option | Unified Logging Replacement | | ------------------------ | --------------------------- | | -XX:+TraceClassLoading | -Xlog:class+load=info | | -XX:+TraceClassUnloading | -Xlog:class+unload=info | | -XX:+TraceExceptions | -Xlog:exceptions=info |

Parts of the Signal-Chaining API Are Deprecated

The signal-chaining facility was introduced in JDK 1.4 and supported three different Linux signal-handling API's: sigset, signal and sigaction. Only sigaction is a cross-platform, supported, API for multi-threaded processes. Both signal and sigset are considered obsolete on those platforms that still define them. Consequently, the use of signal and sigset with the signal-chaining facility are now deprecated, and support for their use will be removed in a future release.

IncompatibleClassChangeError Exceptions Are Thrown For Failing 'final' Checks When Defining a Class

As a result of changes to section 5.3.5 of the Java Virtual Machine Specification, a java.lang.IncompatibleClassChangeError exception is thrown instead of a java.lang.VerifyError exception when defining a class whose super class is final and when defining a class that tries to override a final method.

java.util.logging.LogRecord Updated to Support Long Thread IDs

In this release, java.util.logging.LogRecord has been updated to support long thread ids.

LogRecord::getThreadID and LogRecord::setThreadID are deprecated. New accessors, LogRecord::getLongThreadID and LogRecord::setLongThreadID, are provided and should be used instead.

The serial field threadID has been deprecated and a new serial field longThreadID that can support long values has been introduced. The deprecated threadID field is kept in the serial form for backward compatibility. Long thread ids that are less than Integer.MAX_VALUE are directly mapped to threadID and longThreadID has the same value. For longThreadID greater than Integer.MAX_VALUE, a new negative value for the int threadID is synthesized by using a deterministic algorithm based on the longThreadID hash. The resulting value is guaranteed to be a negative value.

Module::getPackages Returns the Set of Package Names in This Module

Module::getPackages returns the set of package names for the packages in this module.

For unnamed modules, the specification and implementation have been corrected to return the names of the packages defined in the unnamed module. Prior to Java SE 16, Module::getPackages returned the set of package names for the packages defined in the module's class loader if the module was an unnamed module and the result included packages of other named modules defined in the module's class loader, if any.

SUN, SunRsaSign, and SunEC Providers Supports SHA-3 Based Signature Algorithms

SUN, SunRsaSign, and SunEC provider have been enhanced to support SHA-3 based signature algorithms. DSA signatures, RSA, and ECDSA signature implementations with SHA-3 family of digests are now supported through these providers. In addition, RSASSA-PSS signature implementation from SunRsaSign provider can recognize SHA-3 family of digests when specified in signature parameters.

Added 3 SSL Corporation Root CA Certificates

The following root certificates have been added to the cacerts truststore: ``` + SSL Corporation + sslrootrsaca DN: CN=SSL.com Root Certification Authority RSA, O=SSL Corporation, L=Houston, ST=Texas, C=US

• sslrootevrsaca DN: CN=SSL.com EV Root Certification Authority RSA R2, O=SSL Corporation, L=Houston, ST=Texas, C=US

• sslrooteccca DN: CN=SSL.com Root Certification Authority ECC, O=SSL Corporation, L=Houston, ST=Texas, C=US ```

Added -trustcacerts and -keystore Options to keytool -printcert and -printcrl Commands

The -trustcacerts and -keystore options have been added to the -printcert and -printcrl commands of the keytool utility. The -printcert command does not check for the weakness of a certificate's signature algorithm if it is a trusted certificate in the user's keystore or in the cacerts keystore. The -printcrl command verifies the CRL using a certificate from the user's keystore or the cacerts keystore, and will print out a warning if it cannot be verified.

jarsigner Preserves POSIX File Permission and symlink Attributes

When signing a file that contains POSIX file permission or symlink attributes, jarsigner now preserves these attributes in the newly signed file but warns that these attributes are unsigned and not protected by the signature. The same warning is printed during the jarsigner -verify operation for such files.

Note that the jar tool does not read/write these attributes. This change is more visible to tools like unzip where these attributes are preserved.

Upgraded the Default PKCS12 Encryption and MAC Algorithms

The default encryption and MAC algorithms used in a PKCS #12 keystore have been updated. The new algorithms are based on AES-256 and SHA-256 and are stronger than the old algorithms that were based on RC2, DESede, and SHA-1. See the security properties starting with keystore.pkcs12 in the java.security file for detailed information.

For compatibility, a new system property named keystore.pkcs12.legacy is defined that will revert the algorithms to use the older, weaker algorithms. There is no value defined for this property.

Removed Root Certificates with 1024-bit Keys

The following root certificates with weak 1024-bit RSA public keys have been removed from the cacerts keystore: ``` + alias name "thawtepremiumserverca [jdk]"   Distinguished Name: EMAILADDRESS=premium-server@thawte.com, CN=Thawte Premium Server CA, OU=Certification Services Division, O=Thawte Consulting cc, L=Cape Town, ST=Western Cape, C=ZA

• alias name "verisignclass2g2ca [jdk]"   Distinguished Name: OU=VeriSign Trust Network, OU="(c) 1998 VeriSign, Inc. - For authorized use only", OU=Class 2 Public Primary Certification Authority - G2, O="VeriSign, Inc.", C=US

• alias name "verisignclass3ca [jdk]"   Distinguished Name: OU=Class 3 Public Primary Certification Authority, O="VeriSign, Inc.", C=US

• alias name "verisignclass3g2ca [jdk]"   Distinguished Name: OU=VeriSign Trust Network, OU="(c) 1998 VeriSign, Inc. - For authorized use only", OU=Class 3 Public Primary Certification Authority - G2, O="VeriSign, Inc.", C=US

• alias name "verisigntsaca [jdk]"   Distinguished Name: CN=Thawte Timestamping CA, OU=Thawte Certification, O=Thawte, L=Durbanville, ST=Western Cape, C=ZA

```

Added Entrust Root Certification Authority - G4 certificate

The following root certificate has been added to the cacerts truststore: ` + Entrust + entrustrootcag4 DN: CN=Entrust Root Certification Authority - G4, OU="(c) 2015 Entrust, Inc. - for authorized use only", OU=See www.entrust.net/legal-terms, O="Entrust, Inc.", C=US `

Deprecated the java.security.cert APIs That Represent DNs as Principal or String Objects

The following APIs have been deprecated: ` java.security.cert.X509Certificate.getIssuerDN() java.security.cert.X509Certificate.getSubjectDN() java.security.cert.X509CRL.getIssuerDN() java.security.cert.X509CertSelector.setIssuer(String) java.security.cert.X509CertSelector.setSubject(String) java.security.cert.X509CertSelector.getIssuerAsString() java.security.cert.X509CertSelector.getSubjectAsString() java.security.cert.X509CRLSelector.addIssuerName(String) These APIs either take or return Distinguished Names asPrincipalorStringobjects and can cause issues due to loss of encoding information or differences when comparing names across different Principal implementations. All of them have alternative APIs that useX500Principal` objects instead.

Signed JAR Support for RSASSA-PSS and EdDSA

This enhancement includes two main changes:

1. The JarSigner API and the jarsigner tool now support signing a JAR file with an RSASSA-PSS or EdDSA key.

2. Instead of signing the .SF file directly, jarsigner creates a SignerInfo signedAttributes field which contains ContentType, MessageDigest, SigningTime, and CMSAlgorithmProtection. The field will not be generated if an alternative signing mechanism is specified by the jarsigner -altsigner option. Please note that although this field was not generated by jarsigner before this code change, it has always been supported when parsing the signature. This means newly signed JAR files with the field can be verified by earlier JDK releases.

Add InvocationHandler::invokeDefault Method for Proxy's Default Method Support

A new method, invokeDefault, has been added to the java.lang.reflect.InvocationHandler interface to allow a default method defined in a proxy interface to be invoked.

Proxy Classes Are Not Open for Reflective Access

All proxy classes are not open for reflective access in Java SE 16.

Prior to Java SE 16, if java.lang.reflect.Proxy was used to implement only public exported proxy interfaces, the proxy class was generated in an unnamed module which was open for reflective access. In Java SE 16, the proxy class is generated in an exported package in a named module. Programs that assume the private members of a proxy class can be made accessible via setAccessible(true) will fail with InaccessibleObjectException. Proxy classes are already defined in dynamic modules in other cases since Java SE 9. Such programs would already fail when it calls setAccessible(true) to those proxy classes prior to this change.

Day Period Support Added to java.time Formats

A new formatter pattern, letter 'B', and its supporting method have been added to java.time.format.DateTimeFormatter/DateTimeFormatterBuilder classes. The pattern and method translate day periods defined in Unicode Consortium's CLDR (https://unicode.org/reports/tr35/tr35-dates.html#dayPeriods). Applications can now express periods in a day, such as "in the morning" or "at night", not just am/pm. The following example demonstrates translating the day periods: ` DateTimeFormatter.ofPattern("B").format(LocalTime.now()) ` This example produces day period text depending on the time of the day and locale.

US/Pacific-New Zone Name Removed as Part of tzdata2020b

Following the JDK's update to tzdata2020b, the long-obsolete files named pacificnew and systemv have been removed. As a result, the "US/Pacific-New" Zone name declared in the pacificnew data file is no longer available for use.

Information regarding this update can be viewed at https://mm.icann.org/pipermail/tz-announce/2020-October/000059.html

Add Stream.toList() Method

A new method toList has been added to the java.util.Stream interface. This introduces a potential source incompatibility with classes that implement or interfaces that extend the Stream interface and that also statically import a toList method from elsewhere, for example, Collectors.toList. References to such methods must be changed to use a qualified name instead of a static import.

JEP 392: Packaging Tool

Provides the jpackage tool, for packaging self-contained Java applications. The jpackage tool was introduced as an incubating tool in JDK 14 by JEP 343. It remained an incubating tool in JDK 15, to allow time for additional feedback. It has been promoted in JDK 16 from incubation to a production-ready feature. As a consequence of this transition, the name of the jpackage module has changed from jdk.incubator.jpackage to jdk.jpackage.

For further details, see JEP 392.

JEP 389: Foreign Linker API (Incubator)

Introduce an API that offers statically-typed, pure-Java access to native code. This API, together with the Foreign-Memory API (JEP 393), will considerably simplify the otherwise error-prone process of binding to a native library.

For further details, see JEP 389.

JEP 393: Foreign-Memory Access API (Third Incubator)

Introduce an API to allow Java programs to safely and efficiently access foreign memory outside of the Java heap.

For further details, see JEP 393.

JEP 396: Strongly Encapsulate JDK Internals by Default

Strongly encapsulate all internal elements of the JDK by default, except for critical internal APIs such as sun.misc.Unsafe. Allow end users to choose the relaxed strong encapsulation that has been the default since JDK 9.

With this change, the default value of the launcher option --illegal-access is now deny rather than permit. As a consequence, existing code that uses most internal classes, methods, or fields of the JDK will fail to run. Such code can be made to run on JDK 16 by specifying --illegal-access=permit. That option will, however, be removed in a future release.

For further details, please see JEP 396.

LDAP Channel Binding Support for Java GSS/Kerberos

A new JNDI environment property “com.sun.jndi.ldap.tls.cbtype” has been added to enable TLS Channel Binding data in LDAP authentication over SSL/TLS protocol to the Windows AD server. Possible value is “tls-server-end-point” - Channel Binding data is created on the base of the TLS server certificate. See the module description of the java.naming module.

Refine ZipOutputStream.putNextEntry() to Recalculate ZipEntry's Compressed Size

Prior to JDK 16, ZipOutputStream.putnextEntry() would not recalculate the compressed size for a compressed (DEFLATED) entry. This could result in the ZipException, "invalid entry compressed size", being thrown if the current ZLIB implementation being used when ZipOutputStream.putNextEntry() was called differed from the implementation at the time when the entry was added to the original ZIP file.

Starting with JDK 16, if the compressed size has not been explicitly set with the ZipEntry.setCompressedSize(long) method when writing a compressed (DEFLATED) entry, then the compressed size is set to the actual compressed size after deflation.

GZIPOutputStream Sets the GZIP OS Header Field to the Correct Default Value

Prior to JDK 16, GZIPOutputStream set the OS field in the GZIP header to 0 (meaning FAT filesystem), which does not match the default value specified in section 2.3.1.2 of the GZIP file format specification version 4.3 (RFC 1952).

As of JDK 16, the GZIP OS Header Field is set to 255, which is the default value as defined in RFC 1952.

JEP 338: Vector API (Incubator)

Provides an initial iteration of an incubator module, jdk.incubator.vector, to express vector computations that reliably compile at runtime to optimal vector hardware instructions on supported CPU architectures and thus achieve superior performance to equivalent scalar computations.

For further details, see JEP 338.

Removal of Experimental Features AOT and Graal JIT

The Java Ahead-of-Time compilation experimental tool jaotc has been removed. Using HotSpot VM options defined by JEP295 produce a not supported option warning but will otherwise be ignored.

The experimental Java-based JIT compiler, Graal JEP317, has been removed. Attempting to use it produces a JVMCI error: JVMCI compiler 'graal' not found.

Improved CompileCommand Flag

The CompileCommand flag has an option type that has been used for a collection of sub commands. These commands weren't verified for validity so spelling mistakes lead to the command being ignored. They had the form: ` -XX:CompileCommand=option,<method pattern>,<option name>,<value type>,<value> `

All option commands now exist as ordinary commands with this form: ` -XX:CompileCommand=<option name>,<method pattern>,<value> `

The option name is verified and the type is inferred. Helpful error messages are given if the command name doesn't exist, or if the value doesn't match the type of the command. All command names are case insensitive.

The old syntax for option commands can still be used. Verification that the option name, value type, and value is consistent has been added.

All available options can be listed with:

` -XX:CompileCommand=help `

Disable TLS 1.0 and 1.1

TLS 1.0 and 1.1 are versions of the TLS protocol that are no longer considered secure and have been superseded by more secure and modern versions (TLS 1.2 and 1.3).

These versions have now been disabled by default. If you encounter issues, you can, at your own risk, re-enable the versions by removing "TLSv1" and/or "TLSv1.1" from the jdk.tls.disabledAlgorithms security property in the java.security configuration file.

Improve Encoding of TLS Application-Layer Protocol Negotiation (ALPN) Values

Certain TLS ALPN values couldn't be properly read or written by the SunJSSE provider. This is due to the choice of Strings as the API interface and the undocumented internal use of the UTF-8 Character Set which converts characters larger than U+00007F (7-bit ASCII) into multi-byte arrays that may not be expected by a peer.

ALPN values are now represented using the network byte representation expected by the peer, which should require no modification for standard 7-bit ASCII-based character Strings. However, SunJSSE now encodes/decodes String characters as 8-bit ISO88591/LATIN-1 characters. This means applications that used characters above U+000007F that were previously encoded using UTF-8 may need to either be modified to perform the UTF-8 conversion, or set the Java security property jdk.tls.alpnCharset to "UTF-8" revert the behavior.

Improve Encoding of TLS Application-Layer Protocol Negotiation (ALPN) Values

Certain TLS ALPN values couldn't be properly read or written by the SunJSSE provider. This is due to the choice of Strings as the API interface and the undocumented internal use of the UTF-8 character set which converts characters larger than U+00007F (7-bit ASCII) into multi-byte arrays that may not be expected by a peer.

SunJSSE now encodes/decodes String characters as 8-bit ISO88591/LATIN-1 characters. This means applications that used characters above U+000007F that were previously encoded using UTF-8 may need to either be modified to perform the UTF-8 conversion, or set the Java security property jdk.tls.alpnCharset to "UTF-8" revert the behavior.

See the updated guide at https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/alpn.html for more information.

TLS Support for the EdDSA Signature Algorithm

The SunJSSE provider now supports the use of the EdDSA signature algorithm. Specifically SunJSSE may use certificates containing EdDSA keys for server side and client side authentication and may use certificates signed with the EdDSA algorithm. Additionally, EdDSA signatures are supported for TLS handshake messages that require digital signatures.

Removal of Legacy Elliptic Curves

The SunEC provider no longer supports the following elliptic curves that are either obsolete or not implemented using modern formulas and techniques: ` secp112r1, secp112r2, secp128r1, secp128r2, secp160k1, secp160r1, secp160r2, secp192k1, secp192r1, secp224k1, secp224r1, secp256k1, sect113r1, sect113r2, sect131r1, sect131r2, sect163k1, sect163r1, sect163r2, sect193r1, sect193r2, sect233k1, sect233r1, sect239k1, sect283k1, sect283r1, sect409k1, sect409r1, sect571k1, sect571r1, X9.62 c2tnb191v1, X9.62 c2tnb191v2, X9.62 c2tnb191v3, X9.62 c2tnb239v1, X9.62 c2tnb239v2, X9.62 c2tnb239v3, X9.62 c2tnb359v1, X9.62 c2tnb431r1, X9.62 prime192v2, X9.62 prime192v3, X9.62 prime239v1, X9.62 prime239v2, X9.62 prime239v3, brainpoolP256r1 brainpoolP320r1, brainpoolP384r1, brainpoolP512r1 `

To continue using any of these curves, users must find third-party alternatives.

JEP 380: Unix domain sockets

Provides support for Unix domain sockets (AF_UNIX) in the java.nio.channels, SocketChannel, and ServerSocketChannel classes.

See JEP-380 for more information.

See also the following release note for information about the limitations in the support on Windows in JDK16.

Incomplete Support for Unix Domain Sockets in Windows 2019 Server

JEP 380: Unix-Domain Socket Channels has been integrated into JDK 16, but due to a problem with the underlying implementation in Windows 2019 Server, it has been disabled on that platform in this release. The functionality is supported on Linux, macOS and on Windows operating systems whose build number is 18362 or greater. This includes Windows 10 (Version 1903) and newer. There are no known issues with Windows 10 (Version 1903). However, some newer versions of Windows 10 may also show the problem, which affects the ability of some native tools (such as cygwin) to access and delete socket files. Other Java APIs are also affected by the problem, but most native Windows tools are not affected by it. More information can be seen in bugs JDK-8259014 and JDK-8252971. This issue will be resolved in JDK 17 and in a future update to JDK 16.

(fs) NullPointerException Not Thrown When First Argument to Path.of or Paths.get Is null

The var args form of Path.of() and Paths.get() method are changed in this release to throw NullPointerException consistently when the first parameter is null. Historically these methods missed a null check on the first parameter when invoked with more than one parameter.

New jdk.ObjectAllocationSample Event Enabled by Default

A new JFR event, jdk.ObjectAllocationSample, is introduced to allow always-on, low-overhead allocation profiling. The event is enabled in both the default and profile configurations, with a maximum rate of 150 and 300 events/s, respectively. Events jdk.ObjectAllocationInNewTLAB and jdk.ObjectAllocationOutsideTLAB also detail memory allocations, but have comparatively higher overhead. They were previously disabled in the default configuration but are now also disabled in the profile configuration to reduce the overhead further.

The impact of this change can be seen in JDK Mission Control (JMC) 8.0, or earlier releases, where the 'TLAB Allocations' page will be missing data. The recommendation is to upgrade to a later version of JMC when the jdk.ObjectAllocationSample support is available. Meanwhile, it is possible to enable the jdk.ObjectAllocationInNewTLAB and jdk.ObjectAllocationOutsideTLAB events in the JMC recording wizard, or edit the .jfc file manually.

Removal of java.awt.PeerFixer

The non-public class java.awt.PeerFixer has been removed in this release. This class was used to provide deserialization support of ScrollPane objects created prior JDK 1.1.1.

Incorrect behavior matching Unicode linebreaks

The change JDK-8235812 in Java 15 introduced incorrect behavior for matching of the \R Unicode linebreak sequence when using the java.util.regex.Pattern API. The \R sequence should match CR (U+000D) or LF (U+000A) individually, but it should not match an individual CR if it occurs in a CRLF sequence. An example of the erroneous behavior is that the pattern \R{2} matches a CRLF sequence, but it should not. A possible workaround is to match linebreaks using individual characters instead of \R, using negative lookahead to prevent matching of an individual CR within a CRLF sequence. To do this, replace the \R sequence with the following: ` (?:(\u000D\u000A)|((?!\u000D\u000A)[\000A\u000B\u000C\u000D\u0085\u2028\u2029])) ` A simpler sequence can be used if matching all of the Unicode-specified linebreak characters is not required, or if special treatment for the CRLF sequence is not required.

Viewing API Documentation on Small Devices

API documentation generated by the JavaDoc Standard Doclet has been updated so that it can be viewed more easily on small devices.

Eliminating Duplication in Simple Documentation Comments

For many simple methods, the first sentence is often a near duplicate of the text provided for the @return tag. To help avoid such duplication, the @return tag has been enhanced so that it can be used as an inline tag at the beginning of the comment, to provide the text for both the first sentence, and the description of the return value.

Improvements for JavaDoc Search

The interactive search feature in API documentation generated by the JavaDoc Standard Doclet has been improved to find additional matches that differ only in case. This is useful when the exact spelling or capitalization of a name is not known.

For full details on JavaDoc Search, see the link to the JavaDoc Search Specification that is found on at the bottom of the HELP page in any API documentation.

API Documentation Links to Platform Documentation

API documentation generated by the JavaDoc Standard Doclet will now automatically link to the appropriate set of platform classes, based on the value of the --source or --release option.

The behavior can be disabled by using the new --no-platform-links option.

The URLs for the different versions of the platform documentation can be configured by the new --link-platform-properties option.

"Type" Terminology in Generated Documentation

In line with guidelines described elsewhere 1, the Standard Doclet uses the following terms when generating documentation for JDK 16 or later. For consistency, the older terms will continue to be used when generating documentation for older releases.

• Classes and Interfaces (instead of Types)
• Annotation Interface (instead of Annotation Type)
• Enum Class (instead of Enum)
• Record Class (instead of Record)

Line Terminator Definition Changed in java.io.LineNumberReader

The definition of line terminator has been extended to include end of stream, or one of the previously defined line terminators '\n', '\r', or '\r\n' followed immediately by end of stream. This changes behavior in certain cases. For example, a file containing the lines

line 1\n
line 2\n
line 3

would, before this change, have been considered to contain two lines, each terminated by '\n'. After this change, it is considered to contain three lines, the third being terminated by end of stream.

DataInputStream:readFully now correctly throws specified exceptions

DataInputStream.readFully(byte[] b, int off, int len) now correctly throws specified NullPointerException and IndexOutOfBoundsException.

DataInputStream.readFully(byte[] b, int off, int len) is specified to throw a NullPointerException if b is null, and an IndexOutOfBoundsException if off is negative, len is negative, or len is greater than b.length - off. For example if b was null and len was zero, then the method would fail silently without throwing a NullPointerException. Also if b was non-null, off was negative and len was zero, then the method would fail silently without throwing an IndexOutOfBoundsException. The implementation has been corrected to throw the respective exceptions as specified.

Shenandoah: Concurrent weak reference processing

The Shenandoah GC now processes all soft, weak and phantom references as well as finalizers concurrently with the running Java application, instead of at a GC pause. This reduces GC induced latency, especially with workloads that churn many such references or finalizers.

JEP 376: ZGC Concurrent Stack Processing

The Z Garbage Collector now processes thread stacks concurrently. This allows all roots in the JVM to be processed by ZGC in a concurrent phase instead of stop-the-world pauses. The amount of work done in ZGC pauses has now become constant and typically not exceeding a few hundred microseconds.

For further details, see JEP 376.

Concurrently Uncommit Memory in G1

This new feature is always enabled and changes the time when G1 returns Java heap memory to the operating system. G1 still makes sizing decisions during the GC pause, but offloads the expensive work to a thread running concurrently with the Java application.