static-methods

This question already has an answer here: Static Classes In Java 14 answers So, in short. I have two classes. package rpg; public class Engine { public void main(String args[]) { Start.gameStart(); System.out.println(menuResult); } } and package rpg; public class Start { int menuResult = 3; public int gameStart() { return menuResult; } public int getMenuResult() { return Start.menuResult; } } It keeps throwing up the error 'Cannot make static reference to non-static method gameStart()'. I'm sure I'm missing something simple, but can't find it. Thanks! You need to create instance of Start class

It is certainly not for good OOP design - as the need for common behavior of all instances of a derived class is quite valid conceptually. Moreover, it would make for so much cleaner code if one could just say Data.parse(file) , have the common parse() code in the base class and let overriding do its magic than having to implement mostly similar code in all data subtypes and be careful to call DataSybtype.parse(file) - ugly ugly ugly So there must be a reason - like Performance ? As a bonus - are there OOP languages that do allow this ? Java-specific arguments are welcome as that's what I am

What I'm asking is whether there is a difference between doing this: public Something importantBlMethod(SomethingElse arg) { if (convenienceCheckMethod(arg)) { // do important BL stuff } } private boolean convenienceCheckMethod(SomethingElse arg) { // validate something } And this: public Something importantBlMethod(SomethingElse arg) { if (convenienceCheckMethod(arg)) { // do important BL stuff } } private static boolean convenienceCheckMethod(SomethingElse arg) { // validate something } I actually use option 1 as it seems more natural to me. So is there a style/convention/performance

Say that I have a Java project with some "Utils" classes, and that those classes have only static methods and members. Once I run my application, are those methods and members automatically loaded into memory? Or that only happens once I call the class along the code? EDIT: Some sample code to illustrate my question. RandomUtils.java public class RandomUtils { private static Random rand = new Random(); public static int randInt(int min, int max) { // nextInt is normally exclusive of the top value, // so add 1 to make it inclusive return rand.nextInt((max - min) + 1) + min; } } MainClass.java