How to create singleton java class for multiple jvm support?

For example I have DBManager.java Singleton Class, which I have to deploy on clustered environment. It is a web based application, with following deployment stratergy

Apache Load Balancer --> Tomcat 6 (3 Servers in cluster).

I have to maintain single instance of DBManager for 3 tomcat instances.

My code is

package com.db.util;
public class DBManager {
    private static DBManager singleInstance;
    private DBManager () {}
    public static DBManager getSingleInstance() {
        if (singleInstance == null) {
            synchronized (DBManager.class) {
                if (singleInstance == null) {
                    singleInstance = new DBManager ();
                }
            }
        }
        return singleInstance;
    }
}

I have been searching a solution to this problem, and found something like JGroups API. Can this be achieved using JGroups ? Any Idea, How to implement that ?