尽管不能创建Figure类型的对象，但是可以创建Figure类型的引用变量。变量figure被声明为指向Figure对象的引用，这意味着可以使用该变量引用所有派生自Figure的类对象。正如所解释的,正是通过超类引用变量，才能在运行时解析重写方法。-Although you can not create an object Figure type Figure type but you can create a reference variable.  Variable figure is declared as a reference point Figure objects, which means you can use the variable lead 　With all derived　Figure class object. As explained, it is a reference to the superclass variables,

 　Resolved at runtime to override methods.