Fix maven compile config.

Author: javadev

pom-central.xml

@@ -52,8 +52,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.8.1</version>
         <configuration>
-          <source>1.6</source>
-          <target>1.6</target>
+          <source>1.8</source>
+          <target>1.8</target>
           <encoding>UTF-8</encoding>
         </configuration>
       </plugin>