This issue we solved by editing  the file  "dj_make_ubuntu_java_chroot"

In this file we changed oracle java and add to openjdk-8-jdk

PROXYSETTINGS="http_proxy=\"$DEBPROXY\" https_proxy=\"$DEBPROXY\""
chroot "$CHROOTDIR" /bin/sh -c "$PROXYSETTINGS apt-add-repository -y ppa:openjdk-r/ppa"
chroot "$CHROOTDIR" /bin/sh -c "$PROXYSETTINGS apt-get update"
chroot "$CHROOTDIR" /bin/sh -c "$PROXYSETTINGS apt-get install openjdk-8-jdk"

From: "Jaap Eldering" <jaap@jaapeldering.nl>
To: "domjudge-devel" <domjudge-devel@domjudge.org>
Sent: Wednesday, 16 December, 2015 21:11:28
Subject: Re: Switching from Java 1.7 to 1.8 - UnsupportedClassVersionError

Hi Anand,

openjdk-8 is not in Debian Jessie, the Debian version that is used to
build the chroot. It is available in jessie-backports, so you could
manually enter the chroot and then add that archive to the apt sources
and install it.

See the dj_make_chroot script for how to enter the chroot environment
manually (you probably need to mount proc and dev and copy
/etc/resolv.conf to make apt work properly inside it) and see:
http://backports.debian.org/Instructions/

Jaap


On 16-12-15 12:43, Br. Anand Shenoi wrote:
Hi all,
 
 We tried editing chroot file. There is a parameter called INSTALLDEBS="openjdk-8-jre-headless". But it is not picking the jre8 and generated error.
 
 Please resolve this issue.
 
 ________________________________________
 From: DOMjudge-devel <domjudge-devel-bounces@domjudge.org> on behalf of Br. Anand Shenoi <anandam@outlook.com>
 Sent: Wednesday, December 16, 2015 5:18 PM
 To: Tobias Werth; domjudge-devel@domjudge.org; Jaap Eldering; Thijs Kinkhorst
 Subject: Re: Switching from Java 1.7 to 1.8 - UnsupportedClassVersionError
 
 How to do that? In fact we have 1.8 outside, 1.7 inside However, DOMjudge chroot is fetching only 1.7.  Can we change it?
 
 ________________________________________
 From: Tobias Werth <werth@cs.fau.de>
 Sent: Wednesday, December 16, 2015 5:16 PM
 To: Br. Anand Shenoi; domjudge-devel@domjudge.org; Jaap Eldering; Thijs Kinkhorst
 Subject: Re: Switching from Java 1.7 to 1.8 - UnsupportedClassVersionError
 
 Hi,
 
 On 12/16/15 12:45, Br. Anand Shenoi wrote:
Here is an error from a java program:


 Program error output

 Exception in thread "main" java.lang.UnsupportedClassVersionError: SimilarStrings : Unsupported major.minor version 52.0
         at java.lang.ClassLoader.defineClass1(Native Method)
         at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
         at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
         at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
         at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
         at java.security.AccessController.doPrivileged(Native Method)
         at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
         at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

 The JDK in Judgenode is 1.8 whereas chroot in domjudge is fetching only 1.7. Any way to resolve this error?

 
 Install the same Java version inside and outside of the chroot.
 So, either downgrade javac outside to java7 or update it inside to java8.
 
 Cheers,
 Tobi
 
 
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