隐藏Javainheritance中的字段

在类中，与超类中的字段具有相同名称的字段会隐藏超类的字段。

public class Test { public static void main(String[] args) { Father father = new Son(); System.out.println(father.i); //why 1? System.out.println(father.getI()); //2 System.out.println(father.j); //why 10? System.out.println(father.getJ()); //why 10? System.out.println(); Son son = new Son(); System.out.println(son.i); //2 System.out.println(son.getI()); //2 System.out.println(son.j); //20 System.out.println(son.getJ()); //why 10? } } class Son extends Father { int i = 2; int j = 20; @Override public int getI() { return i; } } class Father { int i = 1; int j = 10; public int getI() { return i; } public int getJ() { return j; } } 

有人可以为我解释结果吗？

Answer 1

在java中，字段不是多态的。

 Father father = new Son(); System.out.println(father.i); //why 1? Ans : reference is of type father, so 1 (fields are not polymorphic) System.out.println(father.getI()); //2 : overridden method called System.out.println(father.j); //why 10? Ans : reference is of type father, so 2 System.out.println(father.getJ()); //why 10? there is not overridden getJ() method in Son class, so father.getJ() is called System.out.println(); // same explaination as above for following Son son = new Son(); System.out.println(son.i); //2 System.out.println(son.getI()); //2 System.out.println(son.j); //20 System.out.println(son.getJ()); //why 10? 

Answer 2

根据覆盖和隐藏方法

被调用的隐藏方法的版本取决于它是从超类还是从子类调用。

即，当您通过超类引用调用在子类中重写的方法时，将调用超类方法并访问超类成员。

这解释了以下因为使用的引用是超类：

 System.out.println(father.i); //why 1? System.out.println(father.j); //why 10? System.out.println(father.getJ()); //why 10? 

同样如下：

 System.out.println(son.getJ()); //why 10? 

因为在Son没有定义getJ() ，所以调用了Father类，它看到了在Father类中定义的成员。

如果你读隐藏场 ; 他们特别不推荐这种编码方法

一般来说，我们不建议隐藏字段，因为它使代码难以阅读。