Doble check singleton implementation

Singleton.java

@SuppressWarnings({"unused", "FieldCanBeLocal", "WeakerAccess"})
public final class Singleton {

    private static volatile Singleton ourInstance = null;

    public static Singleton getInstance() {
        if (ourInstance == null) {
            synchronized (Singleton.class) {
                if (ourInstance == null) {
                    ourInstance = new Singleton();
                }
            }
        }
        return ourInstance;
    }

    private Singleton() {
    }
}