How do I implement a Singleton pattern ?

This worked for me:

class Singleton {
    private var val;
    private static var instance;

    private function initialize() {
        val = 42;
    }

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

    function getVal() {
        return val;
    }
}

function testSingleton() {
    var s = Singleton.getInstance();
    System.println("s.getVal() = " + s.getVal());

}