jar

GraalVM native executables can run faster than Scala/Java/JVM applications, with much less memory consumption

In two small tests where GraalVM was able to create a native executable, the native executable ran significantly faster than the equivalent Scala/Java code running with the Java 8 JVM, and also reduced RAM consumption by a whopping 98% in a long-running example. On the negative side, GraalVM currently doesn’t seem to work with Swing applications.

How to create an executable JAR file with `scalac` (and run it with `scala`)

Table of Contents1 - Example2 - A more complex example3 - Problems?4 - Summary

If you’re ever working on a really small Scala project — something that contains only a few source code files — and don’t want to use SBT to create a JAR file, you can do it yourself manually. Let’s look at a quick example. Note that the commands below work on Mac and Linux systems, and should work on Windows with minor changes.

Fixing the Scala error: java.lang.NoSuchMethodError: scala.Product.$init$

As a note to self, when you see a Scala error message that looks like this:

java.lang.NoSuchMethodError: scala.Product.$init$(Lscala/Product;)V

it probably means that you have a mismatch in the Scala versions you’re using in your project. For instance, I just tried to use a library I compiled with Scala 2.12 with Spark, which was compiled with Scala 2.11, and I got that error message. In this case I was able to resolve the problem by recompiling my library with Scala 2.11.

Example: How to use javapackager to build a MacOS application bundle

Table of Contents1 - Building a MacOS application bundle with javapackager2 - The longer story3 - The Mac/Java class4 - The three scripts5 - javapackager notes6 - A “Production” javapackager script

I recently learned how to use the Java javapackager command to build a macOS application bundle — i.e., a regular macOS application — from a Java application. In this tutorial I’ll show how to create a Mac application bundle from a simple Java class, in this case a Java Swing class.

Scala/SBT: How to specify a main method/class to run

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 18.9, “Specifying a Main Class to Run with SBT.”

Problem

In a Scala SBT project, you have multiple main methods in objects in your project, and you want to specify which main method should be run when you type sbt run, or specify the main method that should be invoked when your project is packaged as a JAR file.

Scala/SBT: How to deploy a single, executable Jar file alvin July 10, 2017 - 2:40pm

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 18.14, “How to Deploy a Single, Executable JAR File.”

Problem

You’re building a Scala application, such as a Swing application, and want to deploy a single, executable JAR file to your users.

How to build a macOS application from a Java Jar file

Table of Contents1 - Background2 - Requirements3 - Building your application4 - Note 1: Font smoothing5 - Note 2: Setting the “application category”6 - The Mac/Java AppBundler7 - More information8 - Summary

In this article I’ll show how to build a macOS application from a Java Jar file. I tested this with Java 1.8 on macOS 10.12.5 (Sierra) on June 29, 2017.

Three assumptions in this process are:

How to search multiple jar files for a string or pattern (shell script)

Here’s a Unix shell script that I use to search Java Jar files for any type of string pattern. You can use it to search for the name of a class, the name of a package, or any other string/pattern that will show up if you manually ran jar tvf on each jar file. The advantage of this script — if you’re a Unix, Linux, or Cygwin user — is that it will search through all jar files in the current directory:

How to run a Scala SBT-packaged jar file with Java (the `java` command)

If you want to run/execute a main method from a jar file you created with Scala and the sbt package command, this little tutorial shows how to do it. To make things a little more complicated, my Scala project depends on three external jar files, and the main method requires a command-line argument.

As noted in the Summary, you’ll probably want to use a tool like SBT-Assembly for larger projects.

How to compile, run, and package a Scala project with SBT

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 18.2, “How to compile, run, and package a Scala project with SBT.”

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Problem

You want to use SBT to compile and run a Scala project, and package the project as a JAR file.

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Solution

Create a directory layout to match what SBT expects, then run sbt compile to compile your project, sbt run to run your project, and sbt package to package your project as a JAR file.

Table of Contents

  1. Problem
  2. Solution
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