在向上引用时，子类的同名非静态成员方法与成员变量会覆盖父类的同名非静态成员方法和成员变量，子类的同名静态成员方法会被父类的同名静态成员方法隐藏，也就是说被覆盖。

可以通过 super 关键字在子类中显式调用父类中被覆盖的非静态成员方法和成员变量。

public class Test {
    public static void main(String[] args) {
        System.out.println("Polymorghpic Test");
        Animal a = new Dog();
        Animal b = new Dog("smith", 5);
        // 子类的非静态方法与变量覆盖父类     
        a.getInfo();
        // 子类通过super调用父类的非静态成员方法和变量  
        a.getSuperInfo();
        // 子类的静态方法被父类隐藏   
        a.hello();
        b.getInfo();
        b.hello();
    }
}
class Animal {
    String name;
    int age;
    public Animal() {
        name = "alex";
        age = 1;
    }
    public Animal(String nm, int ag) {
        name = nm;
        age = ag;
    }
    public void getInfo() {
        System.out.print(name + "'s age is " + age + '\n');
    }
    public void getSuperInfo() {}
    public static void hello() {
        System.out.println("Greeting from Animal");
    }
}
class Dog extends Animal {
    String name;
    int age;
    public Dog() {
        name = "prter";
        age = 3;
    }
    public Dog(String nm, int ag) {
        super(nm, ag);
    }
    public void getInfo() {
        System.out.print(name + "'s age is " + age + '\n');
    }
    // 通过super显式调用父类的非静态成员方法   
    public void getSuperInfo() {
        super.getInfo();
    }
    public static void hello() {
        System.out.println("Greeting from Dog");
    }
}

结果：

Polymorghpic Test
prter's age is 3
alex's age is 1
Greeting from Animal
null's age is 0
Greeting from Animal

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