继承 多态 实参形参

package lianxii;

import java.util.Date;

public class Person2 {

    public String name;
    public int    age;
    private Date  birthDate;

    public String getInfo() {

        return "name:" + name + "\nage:" + age;
    }
}
//类Person2
package lianxii;

public class Student2 extends Person2 {

    private String school    = "BeiJing";
    private String className = "errr";

    public String getSchool() {

        return school;
    }

    @Override
    public String getInfo() {

        return super.getInfo() + "\nschool:" + school + "\nclassName:" + className;
    }

    public static void main(String[] args) {

        Student2 y = new Student2();
        y.school = "NanJing11";
        y.className = "ChuYi";
        System.out.println(y.getInfo() + "\n");

        Person2 t = new Person2();
        t.age = 23;
        t.name = "zhong";
        System.out.println(t.getInfo() + "\n");
        //多态的情况下
        Person2 p = new Student2();
        System.out.println(p.getInfo() + "\n");
    }
}
//类Student2
//一个引用类型变量如果声明为父类的类型，但实际引用的是子类对象，那么该变量就不能再访问子类中添加的方法和属性
package lianxii;

public class Test {

    public String method(Person2 r) {//形参

        return r.getInfo();
    }

    public static void main(String[] args) {

        Test u = new Test();
        Student2 p = new Student2();
        u.method(p);//实参
        System.out.println(u.method(p));
    }

}
//测试类Test
//方法声明的参数类型为父类类型，可以使用子类的对象作为实参调用该方法