class Singleton {

    private static Singleton instance = null;

    private Singleton() {
    }    

public static Singleton getInstance() {
    if (instance == null) {
        instance = new Singleton();
    }
    return instance;
}

/**
 *
 * @author Mutasem
 */
public class NewSingleton {
    
    private NewSingleton() {
    }
    
    public static NewSingleton getInstance() {
        return NewSingletonHolder.INSTANCE;
    }
    
    private static class NewSingletonHolder {

        private static final NewSingleton INSTANCE = new NewSingleton();
    }
}

/**
 *
 * @author Mutasem
 */
public class Connection {
    private static Connection instance = null;
    private Connection() {
        try {
            System.out.println("Construction");
            Thread.sleep(2000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Connection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public static Connection getInstance() {
        if (instance == null) {
            instance = new Connection();
        }
        return instance;
    }
    public void connect() {
        System.out.println("Connecting");
    }
}
/******************************************/
/**
 *
 * @author Mutasem
 */
public class Clients {

    public static void main(String[] args) {
        Connection client1 = Connection.getInstance();
        Connection client2 = Connection.getInstance();
        Connection client3 = Connection.getInstance();
        Connection client4 = Connection.getInstance();
        client1.connect();
        client2.connect();
        client3.connect();
        client4.connect();
    }
}

/**
 *
 * @author Mutasem
 */
public class Connection {

    private static Connection instance = null;

    public Connection() {
        try {
            System.out.println("Construction");
            Thread.sleep(2000);
        } catch (InterruptedException ex) {
            Logger.getLogger(Connection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    

    public void connect() {
        System.out.println("Connecting");
    }
}
/******************************************/
/**
 *
 * @author Mutasem
 */
public class Clients {

    public static void main(String[] args) {
        Connection client1 = new Connection();
        Connection client2 = new Connection();
        Connection client3 = new Connection();
        Connection client4 = new Connection();
        client1.connect();
        client2.connect();
        client3.connect();
        client4.connect();
    }
}