Java继承和隐藏的公共字段 [英] Java inheritance and hidden public fields

问题描述

为了模拟一些看起来像这样的自动生成的类，我制作了一个小的jUnit测试类来模拟继承和隐藏字段.

To simulate some auto-generated classes which looks like this, I made a small jUnit test class to simulate inheritance and hidden fields.

public class ClassDerivationTest {

    @Test
    public void testChild() {

        ChildClass child = new ChildClass();

        // Implicit boolean as it is hiding the super value
        child.value = true;

        // one way to update the parent value
        // child.setParentVal("true");

        // child.super.value = "test";
    }

    public class ChildClass extends ParentClass {
        public boolean value;
    }

    public class ParentClass {
        public String name;
        public String value;
    }
}

我的问题是:是否可以通过类似的方式来分配超类value字段的任何简短方法:

My question is: is there any short way to assign the super class value field in a similar way like this:

child.super.value = "test";

而不是在ChildClass中创建特定的设置器:

instead than creating a specific setter in the ChildClass:

    // Imagine this method is not existing for the question
    public void setParentVal(String val) {
        super.value = val;
    }

我正在使用Java 7，我想知道是否可以在不修改ChildClass或ParentClass的情况下进行修改(就像它可能是自动生成的代码一样).

I am using Java 7, and I am wondering if it would be possible without modifying the ChildClass nor the ParentClass (Like it could be auto-generated code).

更新: 我知道您有几种方法可以通过 a)根据乔恩的答案进行投射:((ParentClass) child).value = "test";，但效果不是很好 b)尽可能实例化超类:ParentClass myInstance = new ChildClass(); 代码myInstance.value将引用ParentClass中的字段

UPDATE: I know you there are several ways to manage this by a) Casting according to Jon's answers: ((ParentClass) child).value = "test"; but not very well b) Instanciate the super class like this (as much as possible): ParentClass myInstance = new ChildClass(); The code myInstance.value will refer to the field in ParentClass

但是我想更加关注Java 8的新功能. 例如，是否可以使用lambda或Java 8的另一个新功能来解决此问题?

But I wanted to be more focused on the new features of Java 8. For example is it possible to resolve this with a lambda, or another new feature of Java 8?

推荐答案

好吧，您可以强制转换child来使编译器相对于ParentClass而不是ChildClass来解析字段value:

Well you can just cast child to make the compiler resolve the field value with respect to ParentClass instead of ChildClass:

((ParentClass) child).value = "test";

但坦率地说，我会:a)避免使用非私有字段； b)避免有意识地给同名的超类和子类字段.

But frankly I would a) avoid non-private fields; b) avoid knowingly giving superclasses and subclasses fields with the same name.

与您的评论相反，子类字段不会覆盖"超类字段-它会将其隐藏.

Contrary to your comment, the subclass field doesn't "override" the superclass field - it hides it.

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