抽象类的问题？

Question

public abstract class Shape{}

public class Point extends Shape{
    public Point(double x,double y){
        this.x=x;
        this.y=y
    }
}

现在是这样：

Shape s = new Point(10,10);

如何理解这个实例？

Answer 1

只要看到抽象类的引用，引用的一定是其子类的实例，这里shape是抽象类，引用的是子类Point的实例对象

Answer 2

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

Answer 3

实例化对象的过程就是调用默认构造函数的过程。如果自定义构造函数，系统就不会默认生成。