Update pom

API/pom.xml

@@ -10,12 +10,6 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>API</artifactId>
 
-    <properties>
-        <maven.compiler.source>16</maven.compiler.source>
-        <maven.compiler.target>16</maven.compiler.target>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>com.google.protobuf</groupId>

ensure-java-16

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+JV=`java -version 2>&1 >/dev/null | head -1`
+echo $JV | sed -E 's/^.*version "([^".]*)\.[^"]*".*$/\1/'
+
+if [ "$JV" != 16 ]; then
+	case "$1" in
+	install)
+		echo "Installing SDKMAN..."
+		curl -s "https://get.sdkman.io" | bash
+		source ~/.sdkman/bin/sdkman-init.sh
+		sdk version
+		sdk install java 16.0.1-adpt
+		;;
+	use)
+		echo "must source ~/.sdkman/bin/sdkman-init.sh"
+		exit 1
+		;;
+	esac
+fi

jitpack.yml

@@ -2,9 +2,10 @@ jdk:
   - openjdk16
 before_install:
   - echo "Before Install"
-  - bash ensure-java-16 install
+  - ./ensure-java-16 install
 install:
   - echo "Install"
-  - if ! bash ensure-java-16 use; then source ~/.sdkman/bin/sdkman-init.sh; fi
+  - if ! ./ensure-java-16 use; then source ~/.sdkman/bin/sdkman-init.sh; fi
   - java -version
-  - mvn install
+
+# Thanks to https://github.com/jitpack/jitpack.io/issues/4355#issuecomment-744678253

pom.xml

@@ -23,6 +23,15 @@
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <source>16</source>
+                    <target>16</target>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>