Object variables and class variables in Java

I'm learning Java. I don't understand the difference between object variables and class variables All I know is that in order to make it a class variable, you must first declare it with a static statement@ H_ 419_ 2 @ Thank you!

Solution

In Java (usually OOP), objects have two types of fields (variables)

Instance variables (or object variables) are fields that belong to a specific instance of an object

Static variables (or class variables) are common to all instances of the same class

Here is an example:

public class Foobar{
    static int counter = 0 ; //static variable..all instances of Foobar will share the same counter
    public int id; //instance variable. Each instance has its own id
    public Foobar(){
        this.id = counter++;
    }
}

Usage:

Foobar obj1 = new Foobar();
Foobar obj2 = new Foobar();
System.out.println("obj1 id : " + obj1.id + " obj2.id "= obj2.id + " id count " + Foobar.counter);