一文彻底搞懂父类引用指向子类对象问题

public class Father {
  private String name;
  private int age;
  private int weight;
  public void eat() {
    System.out.println("Father is eating");
  }
  private void run() {
    System.out.println("Runing....");
  }
  public Father() {
    name = "zhangsan";
    age = 23;
    weight = 60;
  }
  public static void main(String[] args) {
    /*
     *
     *如果子类的构造方法中对继承来自父类的变量重新赋予新的值的话，那么这样子调用的将会是子类的变量
     *如果子类重新定义了和父类一样的变量的话那么这样将会输出的是父类的变量  
     *Father f = new Son();
     *f.age f.weight
     */
    Father f = new Son();
    f.eat();
    f.run();
    System.out.println("。。。。。。年龄是：" + f.age + "\t" + f.weight + "\t" + f.name);
//    Son s = new Father();这样子会报错
  }
}
class Son extends Father{
  private int salary;
  public void eat() {
    System.out.println("Son is eating");
  }
  public void sleep() {
    System.out.println("sleep ....");
  }
  public Son() {
    name = "lisi";
    age = 3;
    salary = 60;
    weight = 70;
  }
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    this.age = age;
  }
}