java – 为什么`instanceof`错误而不是在用于2个不兼容的类时返

他们说：

Consider the example program:

class Point { int x,y; }
class Element { int atomicNumber; }
class Test {
        public static void main(String[] args) {
                Point p = new Point();
                Element e = new Element();
                if (e instanceof Point) {       // compile-time error
                        System.out.println("I get your point!");
                        p = (Point)e;           // compile-time error
                }
        }
}

The instanceof expression is incorrect because no instance of Element or any of its possible subclasses (none are shown here) could possibly be an instance of any subclass of Point.

为什么这会导致错误,而不是简单地在返回false的情况下？

谢谢,

JDelage