java继承和多态，对象a = 对象b，调用的是哪个成员变量。

Question

public class Test {
    
    public static void main(String[] args) {
        A a = new A();
        a.s = 11;
        B b = new B();
        b.s = 22;
        a = b;
        System.out.println(a.s);
        System.out.println(b.s);
        System.out.println(a.getS());
        System.out.println(b.getS());
    }
}
class A {
    int s = 1 ;
    int getS() {
        return s;
    }
}

class B extends A {
    int s = 0;
    int getS() {
        return s;
    }
}

输出的是 1 22 22 22
为什么 第一个输出的是1而不是0或者22.按照输出1来看，他调用的是父类A的成员变量s。
这个涉及到了多态，此时a已经指向了men-B，理应输出22，为何输出的是A的成员变量s=1。

Answer 1

The member variable called is determined by the "type of the variable".
A a; If the variable is of type A, it is the variable of type A being called. A a; 变量为A类型就是调用的A类型的变量。
B b; 变量为B类型就是调用的B类型的变量。
多态是跟method相关，跟fieldB b; If the variable is of type B, it is the variable of type B being called.

Polymorphism is related to method and has nothing to do with field. 🎜