fixed build warnings

pom.xml

@@ -25,6 +25,7 @@
 	</developers>
 
 	<properties>
+		<project.build.sourceEncoding>utf-8</project.build.sourceEncoding>
 		<maven.compiler.source>1.7</maven.compiler.source>
 		<maven.compiler.target>1.7</maven.compiler.target>
 		<junit.version>4.13</junit.version>
@@ -43,13 +44,13 @@
 			<!-- This plugin enables the generation of a javadoc JAR -->
 			<plugin>
 				<artifactId>maven-javadoc-plugin</artifactId>
+				<version>3.2.0</version>
 				<executions>
 					<execution>
 						<id>javadoc</id>
 						<phase>package</phase>
 						<goals><goal>jar</goal></goals>
 						<configuration>
-							<detectLinks>true</detectLinks>
 							<show>public</show>
 						</configuration>
 					</execution>