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java-18

README.md

Java 18

To run each example use: java --enable-preview --source 18 <FileName.java>

JEPs

  • 400 - UTF-8 by Default
  • 408 - Simple Web Server
  • 413 - Code Snippets in Java API Documentation
  • 416 - Reimplement Code Reflection with Method Handles
  • 417 - Vector API (Third Incubator)
  • 418 - Internet-Address Resolution SPI
  • 419 - Foreign Function & Memory API (Second Incubator)
  • 420 - Pattern matching for switch (Second Preview)
  • 421 - Deprecate Finalization for Removal

Features

  • Chartset UTF-8 by Default
    • to see which is default: java -XshowSettings:properties -version 2>&1 | grep file.encoding
    • we can change the chartset with property: -Dfile.encoding=UTF-8
    • affected classes:
      • Stream Reader and Writer
      • File Reader and Writer
      • Formatter and Scanner
      • URLEncoder and URLDecoder
    • the System.out and System.err will use the same charset from the terminal
      • we can see with: Console.charset()
  • Pattern Matching for switch (second preview)
    • Minor improvements from JDK 17:
      • refined to use dominance checking that will force constant case label to appear before a guarded pattern of the same type;
      • exhaustiveness checking is now more precise with sealed hierarchies.
  • Code snippet in Java Doc
    • was introduced the @snippet tag to help write code fragments in Java docs
    • the goals is to provide a way to get this fragments (so it can be validated by other tool), enable syntax highlighting and provide better IDE support
    • code snippet suports:
      • attributes (key-pair values like usage="sort")
      • ID to be referred in others snippets (through id attribute)
      • language definition (through lang attribute) - default is java
      • external files (through file attribute) - using external file to define the snippets allow us to use everything that Java supports (like comments with /** */)
    • we can pass --snippet-path to javadoc tool to define the folders for external snippets
    • example:

JVM

  • Reimplemented code reflection to use Method Handles

Links