Fix JDK download URL

travis.sh

@@ -14,7 +14,7 @@ installJdk8() {
   mkdir -p ~/jvm
   pushd ~/jvm > /dev/null
   if [ ! -d "jdk1.8.0_171" ]; then
-    wget --quiet --continue --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz
+    wget --quiet --continue --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u181-b13/96a7b8442fe848ef90c96a2fad6ed6d1/jdk-8u181-linux-x64.tar.gz
     tar xzf jdk-8u171-linux-x64.tar.gz
     rm jdk-8u171-linux-x64.tar.gz
   fi