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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