java多态_成员变量的疑惑

package demo.test;

//父类
class ParentClass {
    public int i = 0;
    
    public void test(){
        System.out.println("ParentClass");
    }

}

public class SubClass extends ParentClass{
    public int i = 1;
    public void test(){
        System.out.println("SubClass");
    }
    
    
    public static void main(String[] args) {
        SubClass     sub1     = new SubClass();
        ParentClass sub2     = new SubClass();
        System.out.println(sub1.i);//1
        System.out.println(sub2.i);//0
        sub1.test();//SubClass
        sub2.test();//SubClass
    }
    /**
     *  1
        0
        SubClass
        SubClass

     */
}