java-18

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

• JDK 18 Jeps