Java

This article is about Java, the programming language.

JDK options

Your default choice should probably be to install jdk11, which is an alias for openjdk11. If you're in a server environment, go for jdk11_headless. Java 11 is the currently-maintained LTS version of OpenJDK as of Oct 2019.

As you might expect, though, many flavors of Java are available in NixOS.

• OpenJDK, by far the most popular non-Oracle JVM implementation
  • openjdk8[_headless] for a legacy Java 8 VM required by some older apps
  • openjdk11[_headless], the currently-supported LTS version of OpenJDK
  • openjdk12[_headless], the current version of OpenJDK
• AdoptOpenJDK, prebuilt binaries for OpenJDK
  • adoptopenjdk-bin points to the latest version of AdoptOpenJDK, which is version 11 at the time of writing.
  • adoptopenjdk-jre-bin is available if you want to avoid downloading the compiler and only require the runtime environment.
• JetBrains JDK (jetbrains.jdk), a fork of OpenJDK with modifications made by JetBrains
• Oracle's JDK (oraclejdk), only version 8 is available.

Using Oracle JDK instead of Open JDK

Almost all Java packages in nixpkgs use Open JDK in form of a jre dependency. If you use Oracle JDK and also want other applications to use it, you can simply tweak your .nixpkgs/config.nix so that your desired application uses Oracles JDK or JRE.

Example with UMLet with JRE

{
  allowUnfree = true;
  packageOverrides = pkgs: rec {
    umlet = pkgs.umlet.override {
      jre = pkgs.oraclejre8;
    };
  };
}

To install the Oracle JRE system-wide, you need to explicitly accept the license in addition to allowing unfree modules:

# /etc/nixos/configuration.nix
{
  nixpkgs.config = {
    allowUnfree = true;
    oraclejdk.accept_license = true;
  };
  environment.systemPackages = with pkgs; [
    oraclejre8
  ];
}

Better font rendering

By default java does not enable antialiasing for font rendering. By exporting environment variables, this can be fixed:

$ export _JAVA_OPTIONS='-Dawt.useSystemAAFontSettings=lcd'

More options can be found in the archlinux wiki