Java 13

To run each example use: java --enable-preview --source 13 <FileName.java>

JEPs

354 - Switch expression (preview 2)
355 - Text blocks (preview)
350 - Dynamic CDS Archives
351 - ZGC: Uncommit Unused Memory
353 - Reimplement the Legacy Socket API

Features

Language

Switch expressions improvements
- Changed break from Java 12 to yield
Text blocks
- flag to compile: -Xlint:text-blocks
API improvements
- String methods:
  - stripIdent: same operation done by the compiler to strip incidental identation from text block';
  - translateEscapes: same operation done by the compiler to translate escapes in strings;
  - formatted: shortcut to String.format '"%s years old".formatted(42))
- NIO improvements
Socket and ServerSocket reimplementation (alignment to Project Loom)

JVM

Creating Class-Data archives For AppCDS
- flag to java -XX:ArchiveClassesAtExit=<FileHere.jsa> to generate class-data on exit
- run with it: -XX:SharedArchiveFile=<FileHere.jsa>
ZGC (Oracle's Z GC) returns unused memory to SO
- -XX:ZUncommitDelay=<seconds> to set the delay in seconds
- -XX:SoftMaxHeapSize: soft (won't generate OutOfMemoryError - will request more) limit to avoid the JVM to grow in memory

Links