How to change Java version of libgdx project?

Question

I'm creating simple game with libgdx java library and can't figure out how to change java version of the project.

Problem: It uses 1.7 and I am trying to change it to 1.8

Things I tried( referring to answer ):

1. Changed sdk version to 1.8 in Project Structure > Project

2. Changed versions of each module in module section

3. Tried to modify build.gradle file to run with 1.8 java

   buildscript {

    repositories { mavenLocal() mavenCentral() gradlePluginPortal() maven { url "https://oss.sonatype.org/content/repositories/snapshots/" } google() } dependencies { classpath 'org.wisepersist:gwt-gradle-plugin:1.1.16' classpath 'org.gretty:gretty:3.0.7' } } allprojects { apply plugin: "eclipse" version = '1.0' ext { appName = "Mario" gdxVersion = '1.11.0' roboVMVersion = '2.3.16' box2DLightsVersion = '1.5' ashleyVersion = '1.7.4' aiVersion = '1.8.2' gdxControllersVersion = '2.2.1' } repositories { mavenLocal() mavenCentral() google() gradlePluginPortal() maven { url "https://oss.sonatype.org/content/repositories/snapshots/" } maven { url "https://oss.sonatype.org/content/repositories/releases/" } maven { url "https://jitpack.io" } } } project(":desktop") { apply plugin: "java-library" // Added apply plugin: "java" sourceCompatibility = 1.8 targetCompatibility = 1.8 dependencies { implementation project(":core") api "com.badlogicgames.gdx:gdx-backend-lwjgl3:$gdxVersion" api "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-desktop" api "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-desktop" } } project(":core") { apply plugin: "java-library" // Added apply plugin: "java" sourceCompatibility = 1.8 targetCompatibility = 1.8 dependencies { api "com.badlogicgames.gdx:gdx:$gdxVersion" api "com.badlogicgames.gdx:gdx-box2d:$gdxVersion" } } project(":html") { apply plugin: "java-library" apply plugin: "gwt" apply plugin: "war" apply plugin: "org.gretty" //Added apply plugin: "java" sourceCompatibility = 1.8 targetCompatibility = 1.8 dependencies { implementation project(":core") api "com.badlogicgames.gdx:gdx-backend-gwt:$gdxVersion" api "com.badlogicgames.gdx:gdx:$gdxVersion:sources" api "com.badlogicgames.gdx:gdx-backend-gwt:$gdxVersion:sources" api "com.badlogicgames.gdx:gdx-box2d:$gdxVersion:sources" api "com.badlogicgames.gdx:gdx-box2d-gwt:$gdxVersion:sources" } }

Answer 1

Your approach of changing the sourceCompatibility to 1.8 is correct, but you did it in the wrong file. There are several build.gradle files in a libgdx project.

In your root directory (where you found the build.gradle file that you mentioned in your question), there is a directory core . Inside this project there is another build.gradle that includes the sourceCompatibility .
The file should look like this:

sourceCompatibility = 1.7 // change to 1.8 here to use java-8 features
[compileJava, compileTestJava]*.options*.encoding = 'UTF-8'

sourceSets.main.java.srcDirs = [ "src/" ]

eclipse.project.name = appName + "-core"