如何在继承中实现封装 [英] how to achieve encapsulation in inheritance

问题描述

我有两个类测试和 Encap 。我有一个私有变量 a 并通过setter和getter方法访问。我继承了测试，其中包含 Encap 。

I have two classes Test and Encap. I have a private variable a and access via setter and getter method. and i'm inheriting the class Test with Encap.

现在我可以使用 setValue（int a）更改 a 的值。我想限制这个选项。我希望它将它作为只读值。请帮助我。

now i am able to change the value of a using setValue(int a). i want to restrict that option. i want it to make it as a read only value. please assist me in this.

class Test
{
    private int a;
    protected void setValue(int a)
    {
        this.a = a;
    }
    protected void getValue()
    {
        System.out.println("The assigned value of a is : "+this.a);
    }
}
public class Encap extends Test {
    public static void main(String [] args)
    {
        Test t = new Test();
        t.setValue(4);
        t.getValue();
        Encap e = new Encap();
        e.setValue(3);
        e.getValue();      
    }
}

推荐答案

一个选项是删除方法 setValue（）来自类测试：

One option would be to delete the method setValue() from the class Test:

class Test
{
    private int a;

    protected void getValue()
    {
        System.out.println("The assigned value of a is : "+this.a);
    }
}

编辑
为什么要这样做？如果 Encap 继承自测试，它应该能够执行与测试相同的操作。否则，继承的目的是什么？如果您仍然认为 Test 应该能够修改该值而 Encap 不是，那么您的设计可能是错误的。您可以尝试这样的事情：

Why to do this? If Encap inherits from Test, it should be able to do the same actions as Test. Otherwise, what's the purpose of inheriting? If you still thinking that Test should be able to modify the value and Encap not, maybe your design is wrong. You could try something like this instead:

              BaseClass
              ---------
              +getValue
                /   \
               /     \
           Test       Encap
         --------   ---------
        +setValue   

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