When to use static methods in Java? Examples and best practices

Hello colleagues! I'm a beginner Java developer, and I'm struggling with the question: when is it correct to use static methods, and when to use regular (instance) methods?\n\nI understand that `static` means the method belongs to the class, not to an object. But in practice, I often get confused. For example, I'm writing a small calculator:\n\n```java\npublic class Calculator {\n public int add(int a, int b) {\n return a + b;\n }\n \n public static int multiply(int a, int b) {\n return a * b;\n }\n}\n```\n\nBoth methods work, but I'm not sure which approach is correct. I've seen that in utility classes (like `Math` or `Collections`), almost all methods are static. But in my own projects, I often see static methods used for factories or singletons.\n\nAnother thing that confuses me: if a method does not use