New APIs in Java 21

Comparing Java 21 (21.0.2+13-LTS-tem) with Java 20 (20.0.2+9-tem).

Element	Modification
java.base
java.io
Console	+ sealed
java.lang.constant
ConstantDescs
BSM_CLASS_DATA	added
BSM_CLASS_DATA_AT	added
CLASS_INIT_NAME	added
INIT_NAME	added
MTD_void	added
ClassDesc
resolveConstantDesc(MethodHandles.Lookup)	added
MethodHandleDesc
resolveConstantDesc(MethodHandles.Lookup)	added
MethodTypeDesc
descriptorString()	+ abstract
of(ClassDesc)	added
of(ClassDesc, List)	added
resolveConstantDesc(MethodHandles.Lookup)	added
ModuleDesc	added
PackageDesc	added
java.lang.foreign
AddressLayout	added preview
Arena
global()	added preview
isCloseableBy(Thread)	removed preview
ofAuto()	added preview
ofConfined()	added preview
ofShared()	added preview
openConfined()	removed preview
openShared()	removed preview
scope()	added preview
scope()	removed preview
GroupLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
Linker.Option.CaptureCallState	removed preview
Linker.Option
captureCallState(String...)	added preview
captureCallState(String...)	removed preview
captureStateLayout()	added preview
isTrivial()	added preview
Linker
downcallHandle(MemorySegment, FunctionDescriptor,...	+ abstract
upcallStub(MethodHandle, FunctionDescriptor,...	added preview
upcallStub(MethodHandle, FunctionDescriptor,...	removed preview
MemoryLayout.PathElement
dereferenceElement()	added preview
groupElement(long)	added preview
MemoryLayout
bitAlignment()	removed preview
bitOffset(MemoryLayout.PathElement...)	removed preview
bitOffsetHandle(MemoryLayout.PathElement...)	removed preview
bitSize()	removed preview
byteAlignment()	+ abstract
valueLayout(Class, ByteOrder)	removed preview
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
MemorySegment.Scope	added preview
MemorySegment
allocateNative(MemoryLayout, SegmentScope)	removed preview
allocateNative(long, SegmentScope)	removed preview
allocateNative(long, long, SegmentScope)	removed preview
array()	removed preview
asSlice(long)	+ abstract
asSlice(long, MemoryLayout)	added preview
asSlice(long, long, long)	added preview
get(AddressLayout, long)	added preview
get(ValueLayout.OfAddress, long)	removed preview
getAtIndex(AddressLayout, long)	added preview
getAtIndex(ValueLayout.OfAddress, long)	removed preview
getAtIndex(ValueLayout.OfBoolean, long)	added preview
getAtIndex(ValueLayout.OfByte, long)	added preview
heapBase()	added preview
isAccessibleBy(Thread)	added preview
ofAddress(long, long)	removed preview
ofAddress(long, long, SegmentScope)	removed preview
ofAddress(long, long, SegmentScope, Runnable)	removed preview
reinterpret(Arena, Consumer)	added preview
reinterpret(long)	added preview
reinterpret(long, Arena, Consumer)	added preview
scope()	added preview
scope()	removed preview
set(AddressLayout, long, MemorySegment)	added preview
set(ValueLayout.OfAddress, long, MemorySegment)	removed preview
setAtIndex(AddressLayout, long, MemorySegment)	added preview
setAtIndex(ValueLayout.OfAddress, long,...	removed preview
setAtIndex(ValueLayout.OfBoolean, long, boolean)	added preview
setAtIndex(ValueLayout.OfByte, long, byte)	added preview
PaddingLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
SegmentAllocator
allocate(AddressLayout, MemorySegment)	added preview
allocate(ValueLayout.OfAddress, MemorySegment)	removed preview
nativeAllocator(SegmentScope)	removed preview
SegmentScope	removed preview
SequenceLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
StructLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
SymbolLookup
libraryLookup(Path, Arena)	added preview
libraryLookup(Path, SegmentScope)	removed preview
libraryLookup(String, Arena)	added preview
libraryLookup(String, SegmentScope)	removed preview
or(SymbolLookup)	added preview
UnionLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
VaList.Builder	removed preview
VaList	removed preview
ValueLayout.OfAddress	removed preview
ValueLayout.OfBoolean
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfByte
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfChar
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfDouble
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfFloat
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfInt
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfLong
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout.OfShort
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
ValueLayout
withBitAlignment(long)	removed preview
withByteAlignment(long)	added preview
withoutName()	added preview
java.lang.invoke
ClassSpecializer.Factory	removed
ClassSpecializer.SpeciesData	removed
StringConcatFactory
MAX_INDY_CONCAT_ARG_SLOTS	added preview
makeConcatWithTemplate(List, List)	added preview
makeConcatWithTemplateCluster(List, List, int)	added preview
makeConcatWithTemplateGetters(List, List, int)	added preview
VarHandle
isAccessModeSupported(VarHandle.AccessMode)	- final
java.lang.reflect
ClassFileFormatVersion
RELEASE_21	added
java.lang.runtime
SwitchBootstraps	- preview
TemplateRuntime	added preview
java.lang
Character
isEmoji(int)	added
isEmojiComponent(int)	added
isEmojiModifier(int)	added
isEmojiModifierBase(int)	added
isEmojiPresentation(int)	added
isExtendedPictographic(int)	added
Class
isUnnamedClass()	added preview
Compiler	removed
FdLibm.Cbrt	removed
FdLibm.Hypot	removed
FdLibm.Pow	removed
MatchException	- preview
Math
clamp(double, double, double)	added
clamp(float, float, float)	added
clamp(long, int, int)	added
clamp(long, long, long)	added
ScopedValue.Carrier	added preview
ScopedValue	added preview
StrictMath
clamp(double, double, double)	added
clamp(float, float, float)	added
clamp(long, int, int)	added
clamp(long, long, long)	added
StringBuffer	+ implements Appendable
repeat(CharSequence, int)	added
repeat(int, int)	added
StringBuilder	+ implements Appendable
repeat(CharSequence, int)	added
repeat(int, int)	added
String
indexOf(String, int, int)	added
indexOf(int, int, int)	added
splitWithDelimiters(String, int)	added
ThreadGroup
allowThreadSuspension(boolean)	removed
Thread
isVirtual()	- preview
ofPlatform()	- preview
ofVirtual()	- preview
startVirtualThread(Runnable)	- preview
StringTemplate.Processor.Linkage	added preview
StringTemplate.Processor	added preview
StringTemplate	added preview
Thread.Builder.OfPlatform	- preview
allowSetThreadLocals(boolean)	removed
Thread.Builder.OfVirtual	- preview
allowSetThreadLocals(boolean)	removed
Thread.Builder	- preview
allowSetThreadLocals(boolean)	removed
java.nio.channels
FileChannel
map(FileChannel.MapMode, long, long, Arena)	added preview
map(FileChannel.MapMode, long, long, SegmentScope)	removed preview
java.security.cert
CertStore
getDefaultType()	+ final
java.util.concurrent
ConcurrentSkipListMap
putFirst(Object, Object)	added
putLast(Object, Object)	added
ConcurrentSkipListSet
addFirst(Object)	added
addLast(Object)	added
CopyOnWriteArrayList
addFirst(Object)	added
addLast(Object)	added
getFirst()	added
getLast()	added
removeFirst()	added
removeLast()	added
reversed()	added
DelayQueue
remove()	added
Executors
newThreadPerTaskExecutor(ThreadFactory)	- preview
newVirtualThreadPerTaskExecutor()	- preview
StructureViolationException	added preview
StructuredTaskScope.ShutdownOnFailure	added preview
StructuredTaskScope.ShutdownOnSuccess	added preview
StructuredTaskScope	added preview
StructuredTaskScope.Subtask.State	added preview
StructuredTaskScope.Subtask	added preview
java.util.regex
Pattern
splitWithDelimiters(CharSequence, int)	added
java.util
ArrayList
addFirst(Object)	added
addLast(Object)	added
getFirst()	added
getLast()	added
removeFirst()	added
removeLast()	added
Arrays	+ final
Collections
newSequencedSetFromMap(SequencedMap)	added
shuffle(List, RandomGenerator)	added
unmodifiableSequencedCollection(SequencedCollectio...	added
unmodifiableSequencedMap(SequencedMap)	added
unmodifiableSequencedSet(SequencedSet)	added
FormatProcessor	added preview
LinkedHashMap	- implements Map + implements SequencedMap
putFirst(Object, Object)	added
putLast(Object, Object)	added
reversed()	added
sequencedEntrySet()	added
sequencedKeySet()	added
sequencedValues()	added
LinkedHashSet	- implements Set + implements SequencedSet
addFirst(Object)	added
addLast(Object)	added
getFirst()	added
getLast()	added
removeFirst()	added
removeLast()	added
reversed()	added
LinkedList
reversed()	added
Locale
availableLocales()	added
caseFoldLanguageTag(String)	added
TreeMap
putFirst(Object, Object)	added
putLast(Object, Object)	added
TreeSet
addFirst(Object)	added
addLast(Object)	added
Deque	+ implements SequencedCollection
reversed()	added
List	- implements Collection + implements SequencedCollection
addFirst(Object)	added
addLast(Object)	added
getFirst()	added
getLast()	added
removeFirst()	added
removeLast()	added
reversed()	added
NavigableMap
reversed()	added
NavigableSet
removeFirst()	added
removeLast()	added
reversed()	added
SequencedCollection	added
SequencedMap	added
SequencedSet	added
SortedMap	- implements Map + implements SequencedMap
putFirst(Object, Object)	added
putLast(Object, Object)	added
reversed()	added
SortedSet	+ implements SequencedSet
addFirst(Object)	added
addLast(Object)	added
getFirst()	added
getLast()	added
removeFirst()	added
removeLast()	added
reversed()	added
javax.crypto
DecapsulateException	added
KEM.Decapsulator	added
KEM.Encapsulated	added
KEM.Encapsulator	added
KEM	added
KEMSpi.DecapsulatorSpi	added
KEMSpi.EncapsulatorSpi	added
KEMSpi	added
javax.net.ssl
KeyManagerFactory
getDefaultAlgorithm()	+ final
TrustManagerFactory
getDefaultAlgorithm()	+ final
java.compiler
javax.lang.model.element
TypeElement
isUnnamed()	added preview
VariableElement
isUnnamed()	added preview
javax.lang.model
SourceVersion
RELEASE_21	added
java.desktop
javax.swing.plaf.synth
SynthComboBoxUI
getMinimumSize(JComponent)	added
SynthLookAndFeel
load(URL)	+ deprecated + forRemoval
javax.swing.text.html
AccessibleHTML.HTMLAccessibleContext
setElementInfo(AccessibleHTML.ElementInfo)	added
java.management.rmi
javax.management.remote.rmi
RMIIIOPServerImpl	removed
java.management
javax.management.remote
JMXConnector
getMBeanServerConnection(Subject)	+ deprecated + forRemoval
java.net.http
java.net.http
HttpClient	+ implements AutoCloseable
awaitTermination(Duration)	added
close()	added
isTerminated()	added
shutdown()	added
shutdownNow()	added
java.xml.crypto
javax.xml.crypto.dsig
SignatureMethod
ED25519	added
ED448	added

Data Source

This report is based on simple comparison of all public and protected APIs of the java.* and javax.* packages of JDK builds 21.0.2+13-LTS-tem and 20.0.2+9-tem. It does not make statements about compatibility.

For the latest Java versions the corresponding CSRs (Compatibility & Specification Review) are linked for a quick reference to find out about the reasoning of the change.

More detailed API comparisons based on the japicmp tool can be found here.