正确答案是

class SingletonLazy {

    private static SingletonLazy singletonLazy;

    private SingletonLazy() {

    }

    public static SingletonLazy getInstance() {
        try {
            if (null == singletonLazy) {
                // 模拟在创建对象之前做一些准备工作
                Thread.sleep(1000);
                synchronized (SingletonLazy.class) {
                    if(null == singletonLazy) {
                        singletonLazy = new SingletonLazy();
                    }
                }
            }
        } catch (InterruptedException e) {
            // TODO: handle exception
        }
        return singletonLazy;
    }
}