构造器和多态

//编译失败
class Grandfather{
    int tag=0;

    public Grandfather(int tag) {
        this.tag = tag;
    }
}

class Father extends Grandfather{
    public Father() {
        super(1);//去掉这一句，则默认调用基类无参构造函数，编译失败
        System.out.println("father");
    }
}

//1.1导出类会按照继承层次逐渐向上调用基类构造器,1.2然后按照声明顺序调用成员初始化方法，1.3最后调用导出类构造器主题；

class Grandfather{
    int tag=0;

    public Grandfather(int tag) {
        System.out.println("ground father");
        this.tag = tag;
    }
}

class Father extends Grandfather{
    public Father() {
        super(1);
        System.out.println("father");
    }
}

class Son extends Father{
    public Son() {
        System.out.println("son");
    }
}

public class Demo01 {
    public static void main(String[] args) {
        new Son();
    }
}

output：
    ground father
    father
    son

class father{
    public father() {
        func();
    }

    void func(){ }
}

class son extends father{
    int tag=1;

    public son(int tag) {
        // System.out.println("tag = "+tag);这里默认调用了父类的构造方法；
        this.tag = tag;
        System.out.println("tag = "+tag);
    }
    
    @Override
    void func() {
        System.out.println("tag = "+tag);
    }
}
public class Demo02 {
    public static void main(String[] args) {
        new son(1);
    }
}

output:
    tag = 0//分配给对象的存储空间初始化为二进制的零；
    tag = 1