scala如何对待伴侣对象？

在java中我们想要在类的不同对象之间共享任何字段.我们声明该字段是静态的.

class Car {
 static NO_Of_TYRES = 4;
 // some implementation.
public int getCarNoOftyres(){
       NO_Of_TYRES; // although it's not a good practice to use static without class name
                    //but we can directly access static member in same class  . 
  }


}

但是在Scala中我们不能在类中声明静态字段,我们需要使用对象(伴随对象).
在scala我们会这样做,

class Car {
 println(NO_Of_TYRES); // scala doesn't let us do that. gives error 
 println(Car.NO_Of_TYRES);// this is correct way. 

}

object Car {
 val NO_Of_TYRES: Int = 4;
}

我只是好奇,scala如何对待伴侣对象？
这两个关键词(类和对象)有什么不同？
为什么scala不允许我们直接在课堂上访问NO_Of_TYRES？