What's new in JDK 14(my short version)

Oracle Release Notes
Java SE 14 Final Release Specification
Java API Diff page: +,-,change

New Features and Enhancements

- Pattern matching instanceof
Examples(from JEP 305):
if (obj instanceof String s) {
    // can use s here
} else {
    // can't use s here
}

@Override public boolean equals(Object o) {
    return (o instanceof CaseInsensitiveString cis) &&
        cis.s.equalsIgnoreCase(s);
}

- Switch Expressions from JDK12 and JDK13 made Standard.

- Text Blocks, second preview, adding 2 new escape sequences:
    \ - line-terminator
    \s - single space

- core-libs: Accounting Currency Format Support, NumberFormat.getCurrencyInstance(Locale)

- core-libs/java.lang: JEP 359 Records (Preview) - data carrier classes.
Example:
record Point(int x, int y) { }
record (name)(state description -> i.e. components of the record) {}
More info:
    * A private final field for each component of the state description;
    * A public read accessor method for each component of the state description, with the same name and type as the component;
    * A public constructor, whose signature is the same as the state description, which initializes each field from the corresponding argument;
    * Implementations of equals and hashCode that say two records are equal if they are of the same type and contain the same state; and
    * An implementation of toString that includes the string representation of all the record components, with their names.
    * Records are final, non-abstract and cannot extend other class and cannot declare instance fields other than the private final fields of state description.
    * Components are final
    * isRecord method added to Class

- RecordComponent class added, that provides information about, and dynamic access to, a component of a record class
- RecordComponentElement interface added, representing a record component.
- TypeElement getRecordComponents method added.
- hotspot/gc: JEP 365 ZGC on Windows. The Z Garbage Collector (ZGC) is now available as an experimental feature on Windows
- hotspot/gc: JEP 364 ZGC on macOS. The Z Garbage Collector (ZGC) is now available as an experimental feature on macOS.
- hotspot/gc: Parallel GC Improvements. Parallel GC has adopted the same task management mechanism for scheduling parallel tasks as other collectors. This might result in significant performance improvements.
- hotspot/jfr: JEP 349 JFR Event Streaming. JDK Flight Recorder (JFR) now supports continuous monitoring of a Java application by allowing events to be consumed dynamically using a new API located in the jdk.jfr.consumer package.
- StrictMath added decrementExact, incrementExact and negateExact for int and long.
- PrintStream added write(byte[]) and writeBytes(byte[]) methods, equivalent to write(buf, 0, buf.length). One has throws, the other does not.

- Added optional @Serial annotation, for annotating methods or fields, to help compiler.
This annotation will check the following:
Your methods are one of the following:
    * private void writeObject(java.io.ObjectOutputStream stream) throws IOException
    * private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException
    * private void readObjectNoData() throws ObjectStreamException
    * ANY-ACCESS-MODIFIERObject writeReplace() throws ObjectStreamException
    * ANY-ACCESS-MODIFIERObject readResolve() throws ObjectStreamException
Your fields are one of the following:
    * private static final ObjectStreamField[] serialPersistentFields
    * private static final long serialVersionUID

- HashSet added new method: toArray()
- LockSupport added setCurrentBlocker(Object) method.

- xml/jaxp: New Method to SAX ContentHandler for Handling XML Declaration
- tools/javac: Allow Discoverable javac Plugins to be Invoked by Default
- security-libs/javax.xml.crypto: Apache Santuario Library Updated to Version 2.1.4
- security-libs/java.security: Weak Named Curves in TLS, CertPath, and Signed JAR Disabled by Default.
- hotspot/gc: JEP 345 NUMA-Aware Memory Allocation for G1.
- core-libs/java.nio: Clarify the Specification of ReadableByteChannel.read() and Related Methods

Removed Features and Options

- hotspot/gc: JEP 363 Remove the Concurrent Mark and Sweep (CMS) Garbage Collector (JEP 363)
- core-libs/java.nio.charsets: Removal of sun.nio.cs.map System Property
- deploy: Removal of netscape.javascript.JSObjectgetWindow Method
- security-libs/java.security: Removed Deprecated java.security.acl APIs
- security-libs/java.security: Removal of the Default keytool -keyalg Value
- tools/jar: JEP 367 Remove the Pack200 Tools and API

Deprecated Features and Options, Other Notes and Differences between Oracle JDK and OpenJDK not included