Question

“Static methods may not communicate with instance fields, only static fields”. I got to read this quoted lines. When I studied other threads in this forum, I found that we can use instance fields in static methods and vice versa. So, what does this quote means?? Is it true?

Answer 1

You can’t use non-static (instance) fields in static method. That’s because a static method is not associated with an instance.

A static method is one-per-class, while a class may have many instances. So if you have 2 instances, the fields of which one will the static methods see?

Let’s imagine that this is valid:

class Foo {
   private int bar;

   public static int getBar() {
      return bar; // does not compile;
   }
}

And then:

Foo foo1 = new Foo();
foo1.bar = 1;
Foo foo2 = new Foo();
foo2.bar = 2;

Foo.getBar(); // what would this return. 1 or 2?