- INTELLIJ CHANGE JAVA VERSION HOW TO
- INTELLIJ CHANGE JAVA VERSION UPGRADE
- INTELLIJ CHANGE JAVA VERSION CODE
This “9” folder only needs to contain the class files for those classes with specific Java 9 features. If you look at the specification, you’ll see that what you need is an output structure that looks something like this:īasically, you have a standard JAR file with all the classes from your application in the root like usual, and an additional “versions” folder in META-INF with specific implementations for each of the additional supported versions of Java (in this case, just Java 9). My project consists of a Main class, an interface to define what I might be interested in about the stack, StackInfo, and an implementation of this interface, StackParser: I’m going to create a really simple application that just outputs the current stack trace (you’ll see why I’ve chosen this example later).
INTELLIJ CHANGE JAVA VERSION HOW TO
However, I wanted to experiment with multi-release JAR files and managed to build them using IntelliJ IDEA, and hope that showing this process helps people to understand how to build multi-release JAR files and how they work. I highly recommend that you do not use the IDE for creating production-ready builds of your application, I expect most people are using Maven, Gradle, Ant or some other build tool. In this blog post I’m going to show how to create a multi-release JAR file in IntelliJ IDEA. The reason for this split, of course, is that Java 8 itself can’t decide what to do differently when it runs a multi-release JAR file because the functionality only became available in Java 9. This is a little bit sad since obviously Java 8 had some nice features that you might want if you’re running Java 8, but the pre-Java-9 support for a library might target 6 onwards like a lot of libraries still do.
This works for Java 9 onwards – so these multi-release JAR files will support a Java 9 version, a Java 10 (or 18.3), 11, 12 version etc… but anything before Java 9 is lumped into “pre-Java 9”. If you’re running it on a version before Java 9, you get the pre-Java-9 implementation.If you’re running it on Java 9, uses Java 9 features and functionality.Now, a library developer can release a single JAR file that:
INTELLIJ CHANGE JAVA VERSION UPGRADE
They either involve a lot of work, or they alienate/confuse users, or the libraries don’t get to make use of new features (and therefore don’t provide much incentive for their users to upgrade their version of Java either).Īs of Java 9, there’s an alternative. None of these approaches is particularly fun for the library developers or their users.
For many library developers, this means they are still compiled against Java 6 and cannot move to using Java 8 features like lambdas and streams until practically all their users have moved to 8 already.
INTELLIJ CHANGE JAVA VERSION CODE
Of course if you use properties, let's say you put in the pom 1.8, then if you use a 1.8 JDK in Intellij(the language level default is 1.8 or the language default was changed manually), then you will be able to code in 1.8 BUT at the mvn compile, the properties will NOT be seen and you will default to Maven 1.One of the interesting features of Java 9 is support for Multi-Release JAR Files. Most of the time you will not downgrade the version of the JDK to 1.4! (the jdk of Intellij is 1.8) and the language level of the project was changed accordingly to 1.4: In the code below, 1.4 was configured in the pom using maven-compiler-plugin The properties do not always change the language level of Intellij! To change the language level, make usage of 'maven-compiler-plugin' ALWAYS work! It is what I suggest you to use.
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