MNEMONIC-641: [JDK14] Specify JDK14 to build project in Maven

Signed-off-by: Zhen Li <rhythmwind@gmail.com>
diff --git a/pom.xml b/pom.xml
index 8ae8007..faf05cc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -97,7 +97,7 @@
   </modules>
 
   <properties>
-    <java.version>1.8</java.version>
+    <java.version>14</java.version>
     <maven.compiler.source>${java.version}</maven.compiler.source>
     <maven.compiler.target>${java.version}</maven.compiler.target>
     <maven.min-version>3.2.1</maven.min-version>
@@ -359,7 +359,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-compiler-plugin</artifactId>
-          <version>3.3</version>
+          <version>3.8.1</version>
           <configuration>
             <source>${java.version}</source>
             <target>${java.version}</target>