Initialization-on-demand holder idiom.java

public class Something {
    private Something() {
        System.out.println("Constructor called...");
    }

    /**
     * SingletonHolder is loaded on the first execution of Singleton.getInstance() or the first access to SingletonHolder.INSTANCE, not before.
     */
    private static class LazyHolder {
        private static final Something INSTANCE = new Something();
    }

    public static Something getInstance() {
        return LazyHolder.INSTANCE;
    }

    public static String foo() {
        return "bar";
    }
    public static void main(String[] args) {
        System.out.println("started...");
        System.out.println(Something.foo());
        Something something = Something.getInstance();
        System.out.println("end");
    }
}