Java Boundaries

There are different context/scopes in java. Java9 adds module.

• block
• class
• package
• module
• jar
• war/ear/sar/...
• classpath
• maven scopes: compile, runtime, test, optional, provided - https://stackoverflow.com/questions/26975818/what-is-scope-under-dependency-in-pom-xml-for
• test/app
• jvm

References

• http://blog.vavr.io/i-believe-in-java-modules/

Advice

• jdk1-jdk7 too old
• xxxJdk8 - is LTS(long term support) but depends on vendor
• OracleJdk8 - no security updates or commercial license
• AdoptOpenJdk8 - $free (libre and gratis) and LTS
• xxxJdk9, xxxJdk10 - don't use it, no LTS deprecated by xxxJdk11
• OracleJdk11 - don't use it, commercial license
• AdoptOpenJdk11 - $free (libre and gratis) and LTS
• OpenJdk11 - $free (libre and gratis) and LTS

References

• https://blog.joda.org/2018/08/java-is-still-available-at-zero-cost.html

Short Timeline

For a longer version go to wikipedia - https://en.wikipedia.org/wiki/Java_version_history

• jdk1.0
• jdk1.2
• jdk5 - generics added => much better collections
• jdk6
• jdk7
• jdk8 - lambda added => much better collections, functional aspects
• jdk9 - modules added => much better overall design
• jdk10
• jdk11 - Oracle asks for commercial license => you should switch to OpenJDK (not Oracle OpenJDK)
  • https://blog.joda.org/2018/09/do-not-fall-into-oracles-java-11-trap.html
  • Oracle JDK11 - don't use it
  • OpenJDK11 - GPL 2 with the Classpath Exception - https://jdk.java.net/11/ - can be used commercially $free
  • others - https://blog.joda.org/2018/09/time-to-look-beyond-oracles-jdk.html

Binaries

• jre & jdk
  • openjdk - https://jdk.java.net/ : Java SE openjdk7, openjdk8, openjdk9, openjdk10, openjdk11
  • adoptopenjdk - https://adoptopenjdk.net/: adoptOpenJdk8, adoptOpenJdk9, adoptOpenJdk10, adoptOpenJdk11 (in progress at 2018-10-01)
  • oracle - never download from oracle.com any jdk anymore (particularly starting with jdk11)
• docker images
  • openjdk - https://hub.docker.com/_/openjdk/
  • adoptopenjdk - https://hub.docker.com/u/adoptopenjdk/

Implementations

• cloud, containers & microservices comparison
  • http://royvanrijn.com/blog/2018/05/openj9-jvm-shootout/
• jdk8
  • jetbrains builds (used in intelij)
    • https://github.com/JetBrains/jdk8u
    • https://bintray.com/jetbrains/intellij-jdk/openjdk8-windows-x64#files/
    • https://intellij-support.jetbrains.com/hc/en-us/community/posts/205991644-Using-JetBrains-64-bit-Runtime-as-JRE-JDK-on-Windows

Path vs classpath

Classpath vs path/file

Locatii resurse

• path absolut - /.....
  • nu controlezi mediul
• path relativ
  • nu controlezi packagingul final: local, multijar classpath, single jar claspath, docker, ....
• classpath
  • este fix, decis la compile time
• path absolut definit de environment variables
  • PRO - content can be dynamically changed
  • CONS - must be provided

Resources

• https://zeroturnaround.com/rebellabs/developer-productivity-report-2017-why-do-you-use-java-tools-you-use/