Intellij - Unable to use newer Java 8 classes - Error : “Usage of API documented as @since 1.6+..”

Question

I\'m trying to use a java.lang.function.Function in my java 8 code base, but i keep getting the following error in Intellij.

Usage of API

Answer 1

Maybe your config of repository has properties include compiler Version. examine settings.xml file.

<jdk>1.8</jdk>
</activation>
<properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
</properties>

Answer 2

I just fixed it as follows:

Right click the project -> Open Module Settings -> Modules -> Sources -> 8 or higher

And then

If still encounter the error and using maven, you have to add the build configuration in your pom.xml:

<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>