well, you could do it the easy way and have jenkins install it and the jdk for you.. but thats not what nerds to is it.
sudo apt-get install openjdk-7-jdk
sudo apt-get install ant
but since there is already a jre only version of a previous java in the system, ant does not find tools.jar and we need to configure the JDK7 as the default java
sudo update-alternatives –config java
then in the menu the choice is the JDK7 version
after this ant works. sweet.