use -source 7 or higher to enable diamond operator

Question

I am trying to build a project using maven, and I am getting this error "diamond operator is not supported in -source 1.6"

I have Java 8 installed and I don't even have Java 6 installed. Please help me.

Thank you.

Answer 1

In maven, there are two ways to set the compiler source and target.

The 1st way is by setting defining those properties values :

<properties>
  <maven.compiler.source>1.8</maven.compiler.source>
   <maven.compiler.target>1.8</maven.compiler.target>
</properties>

The 2nd way is to define the source and the target in the compiler plugin configuration :

 <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.7.0</version>
    <configuration>
      <source>1.8</source>
      <target>1.8</target>
    </configuration>
  </plugin>

And last but not least, make sure that your IDE (Eclipse, Intellij, etc) is properly configured to use Java 8.

Answer 2

You must tell maven in the pom.xml which versionof java to compile to. Specify it like this :

<project>
  [...]
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
  [...]
</project>

See https://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html for more information.