Create single Database connection

I would like to create a single Database connection point that I can
use for 4 classes in my Java Web Application.

Here is my ConnectionManager Class:

public class ConnectionManager {
    private static Connection activeConnection = null;
    public static Connection getConnection() {
        if (activeConnection = null) {
            Class.forName("OracleThinInfoHere...");
            activeConnection =
DriverManager.getConnection("jdbc:oracle:thin:@myname:1234:orcl",
"scott", "tiger");
);
        }
        return activeConnection;
    }
}

Now how would I access this in each one of my classes?

For example here is one:

public class MainClass
{

public ConnectionManager.getConnection(),
public Connection connection;

//I tried my db connection as this and it didnt return any results
public MainClass(connection)
{
     this.connection = ConnectionManager.getConnection();
}

public int matcher(BeanClass abc)
{
     try
     {
         new OtherDbClass(connection).insertDbMethod(abc);
     }
     catch(Exception e)
     {
         e.printStackTrace();
     }
     finally
     {
        //closing statements here
     }

OtherClass looks like this:
public class OtherClass {
   private Connection connection;
   public OtherClass(Connection connection)
   {
      this.connection = ConnectionManager.getConnection();
   }

public int insertDbMethod(BeanClass abc)
{
....
}

Please advise.