多态

 什么是多态

我们用程序说话

代码如下：

package Day07; public class DynamicBindingDemo {
public static void main(String[] args) {
m(new GraduateStudent());
m(new Student());//等价于Object x = new Student(); m(x);
m(new Person1());
m(new Object());
}
public static void m(Object x) {
System.out.println(x.toString());
}
}
class GraduateStudent extends Student {

}
class Student extends Person1 {
public String toString() {
return "Student extends Person1 ";
}
}
class Person1 {
public String toString() {
return "Person1 extends Object";
}
}