By default, Maven assumes you wrote your code using JDK 1.5 and that you want to compile to that same target. You will need to add the maven-compiler-plugin to your build plugins, in order to tell it to use 1.8.
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
Check out the plugin’s docs for more info: http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html