New APIs in Java 21

Comparing Java 21 (21-ea+24-2086-open) with Java 20 (20.0.1+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
of(ClassDesc)	added
of(ClassDesc, List)	added
resolveConstantDesc(MethodHandles.Lookup)	added
ModuleDesc	added
PackageDesc	added
java.lang.foreign
AddressLayout	added preview
Arena
global()	added
isCloseableBy(Thread)	removed
ofAuto()	added
ofConfined()	added
ofShared()	added
openConfined()	removed
openShared()	removed
scope()	added
scope()	removed
GroupLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
Linker.Option.CaptureCallState	removed
Linker.Option
captureCallState(String...)	added
captureCallState(String...)	removed
captureStateLayout()	added
isTrivial()	added
Linker
downcallHandle(MemorySegment, FunctionDescriptor,...	+ abstract
upcallStub(MethodHandle, FunctionDescriptor,...	added
upcallStub(MethodHandle, FunctionDescriptor,...	removed
MemoryLayout.PathElement
dereferenceElement()	added
groupElement(long)	added
MemoryLayout
bitAlignment()	removed
bitOffset(MemoryLayout.PathElement...)	removed
bitOffsetHandle(MemoryLayout.PathElement...)	removed
bitSize()	removed
byteAlignment()	+ abstract
valueLayout(Class, ByteOrder)	removed
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
MemorySegment.Scope	added preview
MemorySegment
allocateNative(MemoryLayout, SegmentScope)	removed
allocateNative(long, SegmentScope)	removed
allocateNative(long, long, SegmentScope)	removed
array()	removed
asSlice(long)	+ abstract
asSlice(long, MemoryLayout)	added
asSlice(long, long, long)	added
get(AddressLayout, long)	added
get(ValueLayout.OfAddress, long)	removed
getAtIndex(AddressLayout, long)	added
getAtIndex(ValueLayout.OfAddress, long)	removed
getAtIndex(ValueLayout.OfBoolean, long)	added
getAtIndex(ValueLayout.OfByte, long)	added
heapBase()	added
isAccessibleBy(Thread)	added
ofAddress(long, long)	removed
ofAddress(long, long, SegmentScope)	removed
ofAddress(long, long, SegmentScope, Runnable)	removed
reinterpret(Arena, Consumer)	added
reinterpret(long)	added
reinterpret(long, Arena, Consumer)	added
scope()	added
scope()	removed
set(AddressLayout, long, MemorySegment)	added
set(ValueLayout.OfAddress, long, MemorySegment)	removed
setAtIndex(AddressLayout, long, MemorySegment)	added
setAtIndex(ValueLayout.OfAddress, long,...	removed
setAtIndex(ValueLayout.OfBoolean, long, boolean)	added
setAtIndex(ValueLayout.OfByte, long, byte)	added
PaddingLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
SegmentAllocator
allocate(AddressLayout, MemorySegment)	added
allocate(ValueLayout.OfAddress, MemorySegment)	removed
nativeAllocator(SegmentScope)	removed
SegmentScope	removed
SequenceLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
StructLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
SymbolLookup
libraryLookup(Path, Arena)	added
libraryLookup(Path, SegmentScope)	removed
libraryLookup(String, Arena)	added
libraryLookup(String, SegmentScope)	removed
or(SymbolLookup)	added
UnionLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
VaList.Builder	removed
VaList	removed
ValueLayout.OfAddress	removed
ValueLayout.OfBoolean
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfByte
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfChar
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfDouble
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfFloat
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfInt
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfLong
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout.OfShort
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
ValueLayout
withBitAlignment(long)	removed
withByteAlignment(long)	added
withoutName()	added
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
java.lang.reflect
ClassFileFormatVersion
RELEASE_21	added
java.lang.runtime
ReferenceKey.SoftKey	added
ReferenceKey.StrongKey	added
ReferenceKey.WeakKey	added
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
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
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
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
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
Digits.DecimalDigits	added
Digits.HexDigits	added
Digits.OctalDigits	added
FormatItem.FormatItemModifier	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.net.ssl
KeyManagerFactory
getDefaultAlgorithm()	+ final
TrustManagerFactory
getDefaultAlgorithm()	+ final
java.compiler
javax.lang.model.element
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-ea+24-2086-open and 20.0.1+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.