What is a "static class" in Java? Explain with examples

Hello, colleagues! I recently started learning Java and came across the term "static class". I think I understand the concept of "static" for fields and methods — it means they belong to the class, not to an instance. But when it comes to an entire class, I get confused. I tried writing this code: ```java public class Main { public static class Helper { public void printMessage() { System.out.println("Hello from static class!"); } } public static void main(String[] args) { Helper h = new Helper(); h.printMessage(); } } ``` This works. But if I remove the word `static` before `class Helper`, it also works. So what's the difference? And in what situations should I use `static` for a class?