Fix Java 16 compilation.

.github/workflows/build.yml

@@ -14,10 +14,10 @@ jobs:
       - uses: actions/checkout@v2
         with:
           fetch-depth: 0  # Shallow clones should be disabled for a better relevancy of analysis
-      - name: Set up JDK 11
+      - name: Set up JDK 16
         uses: actions/setup-java@v1
         with:
-          java-version: 11
+          java-version: 16
       - name: Cache SonarCloud packages
         uses: actions/cache@v1
         with:

pom.xml

@@ -33,11 +33,11 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <java.version>16</java.version>
-        <powermock.version>2.0.4</powermock.version>
+        <powermock.version>2.0.9</powermock.version>
         <!-- More visible way how to change dependency versions -->
         <spigot.version>1.17-R0.1-SNAPSHOT</spigot.version>
         <bentobox.version>1.17.0-SNAPSHOT</bentobox.version>
-        <level.version>2.5.0</level.version>
+        <level.version>2.6.3</level.version>
         <vault.version>1.7</vault.version>
         <!-- Revision variable removes warning about dynamic version -->
         <revision>${build.version}-SNAPSHOT</revision>
@@ -93,6 +93,12 @@
     </distributionManagement>
 
     <repositories>
+        <repository>
+            <!-- This is a temporary reference as the Maven Shade plugin 
+                that supports Java 16 is not released yet -->
+            <id>maven-snapshots</id>
+            <url>https://repository.apache.org/content/repositories/snapshots/</url>
+        </repository>
         <repository>
             <id>spigot-repo</id>
             <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots</url>
@@ -137,7 +143,7 @@
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
-            <version>3.1.0</version>
+            <version>3.11.2</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -213,16 +219,20 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.1</version>
+                <version>3.7.0</version>
                 <configuration>
-                    <source>16</source>
-                    <target>16</target>
+                    <release>${java.version}</release>
                 </configuration>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>2.22.2</version>
+                <version>3.0.0-M5</version>
+                <configuration>
+                    <argLine>
+                        --illegal-access=permit
+                    </argLine>
+                </configuration>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -238,8 +248,7 @@
                     <show>public</show>
                     <failOnError>false</failOnError>
                     <additionalJOption>-Xdoclint:none</additionalJOption>
-                    <!-- To compile with Java 11, this tag may be required -->
-                    <!-- <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable> -->
+                    <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
                 </configuration>
                 <executions>
                     <execution>
@@ -266,7 +275,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-shade-plugin</artifactId>
-                <version>3.2.1</version>
+                <version>3.3.0-SNAPSHOT</version>
                 <configuration>
                     <minimizeJar>true</minimizeJar>
                     <relocations>