How to use Java polymorphism and examples

1. Concept

Polymorphism is the third major feature of object-oriented after encapsulation and inheritance. It is the parent class reference pointing to the child class object.

2. Format

父类类型 变量名=new 子类类型();

3. Usage conditions

There must be a child-parent class relationship.

4. Example

public class Wine {
    public void drinkWine(){
        System.out.println("===今天我要喝什么酒呢====");
        Wine();
    }
    public void Wine(){
        System.out.println("===看看俺今天能喝啥子哟====");
    }
}
public class JNC extends Wine {
    /**
     * @desc 子类重载父类方法
     *        父类中不存在该方法，向上转型后，父类是不能引用该方法的
     * @param a
     * @return void
     */
    public void drinkWine(String a){
        System.out.println("======今天我要喝剑南春====");
        Wine();
    }
    /**
     * 子类重写父类方法
     * 指向子类的父类引用调用Wine时，必定是调用该方法
     */
    public void Wine(){
        System.out.println("=====剑南春喝上啦，好开森=====");
    }
}
public class Test {
    public static void main(String[] args) {
        Wine a = new JNC();
        a.drinkWine();
        a.Wine();
        Wine b = new Wine();
        b.drinkWine();
        b.Wine();
        JNC c= new JNC();
        c.drinkWine("qq");
    }
}

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