fix: java build by 1.8 version

bin/build.sh

@@ -44,7 +44,7 @@ build-extras(){
 	git pull	
 	echo -n "Begin build extras file ... "
 	cd ${BuildRootDir}/bin
-	javac printJarVer.java
+	javac -source 8 -target 8 -bootclasspath /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/rt.jar -extdirs "" printJarVer.java	
 	echo "done"
 }