实例变量(或对象变量)是属于对象的特定实例的字段.

静态变量(或类变量)对同一个类的所有实例都是常见的.

这里有一个例子：

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++;
    }
}

用法：

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