Specifies the Java release version in the pom.xml files

Used by the Java compile since Java 9

Bootstrap/pom.xml

@@ -20,6 +20,7 @@
                 <configuration>
                     <source>${java.version}</source>
                     <target>${java.version}</target>
+                    <release>${java.release}</release>
                 </configuration>
             </plugin>
             <plugin>
@@ -60,4 +61,4 @@
         </dependency>
     </dependencies>
 
-</project>
+</project>

UltimateStacker/pom.xml

@@ -17,11 +17,12 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.0</version>
+                <version>3.8.1</version>
 
                 <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
+                    <source>${java.version}</source>
+                    <target>${java.version}</target>
+                    <release>${java.release}</release>
                 </configuration>
             </plugin>
 

UltimateStackerAPI/pom.xml

@@ -22,6 +22,7 @@
                 <configuration>
                     <source>${java.version}</source>
                     <target>${java.version}</target>
+                    <release>${java.release}</release>
                 </configuration>
             </plugin>
             <plugin>

pom.xml

@@ -15,6 +15,7 @@
     <properties>
         <revision>2.5.0-DEV</revision>
         <java.version>1.8</java.version>
+        <java.release>8</java.release>
     </properties>
 
     <repositories>