This question concerns the usage of the listDomains(). When I run this piece of code in KVM, it works perfectly fine but throws an array out of bounds exception in Xen. Connect conn=null; conn = new Connect("xen:///", true); int[] id = conn.listDomains(); System.out.println("lD of VM " +id[0]); Answer I'd got: Well, your code assumes that id.length is >= 1, but listDomains() can return an empty array when there are no active domains known to libvirt. So you need to check id.length before accessing any element in the array. Follow up- I tried accessing the length of the array and it's 0 all the time. And there are active domains available. In fact, I'm able to getUUID from the domain name. Other functions work fine too. Am I missing something?Can someone please help me? Thanks!