- Go to File > Settings > Build, Execution, Deployment > Compiler > Java Compiler If on a Mac, it’s under Intellij IDEA > Preferences… > Build, Execution, Deployment > Java Compiler
- Change Target bytecode version to 1.8 of the module that you are working for.
If you are using Maven
Add the compiler plugin to
pom.xml under the top-level
<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> </plugins> </build>
(Hoisted from the comments.)
Note: If you don’t mind reimporting your project, then the only thing you really need to do is change the pom and reimport the project, then IntelliJ will pick up the correct settings and you don’t have to manually change them.