Computer Science Question

Question

  what does a static modifier means, what types of methods should it appear in?

Answer 1

It depends on the context and the programming language, but "static" typically indicates that variable or function belongs to the declaring class, and not to the instance of that class (i.e. object).

For example a static method in Java:

class Circle {

private static final double pi = Math.PI;

private String message = "The circle area is ";

public static double calculateArea(int r) {

return r*r*pi;

}

public String getMessage() {

return this.message + Circle.calculateArea(5);

}

}

In the example above calculateArea() is a static method, the right way to call that is e.g. Circle.calculateArea(3). Because it is static it cannot access the instance variables or method of this class such as "message", but it can access "pi" which is static. In other words static methods have no reference to an instance, therefore they cannot access anything through "this".

On the other hand non-static or instance methods like getMessage() can access both instance and static variables and can call both instance or static methods.

Typical use cases for static variables are constants, for static methods are helper or utility functions that operate on their arguments with no need access the state of the object.

Answer 2

static var retains it's value between calls....

static method... the scope is limited to it's file