java - 动态访问Java类的成员变量

Question

我有 3 个类，它们具有相同的变量名称，但值不同。因此，我尝试根据用户提供的输入初始化公共(public)对象中的类，然后打印相应的值。

public class A {
    public String s1 = "a1";
    public String s2 = "a2";
}

public class B {
    public String s1 = "b1";
    public String s2 = "b2";
}

public class C {
    public String s1 = "c1";
    public String s2 = "c2";
}

//This is not a working code, just a skeleton to express what I am trying to achieve
public class ClassDriver {
    public static void main(String[] args) throws Exception {
        String userInput = "A";
        //If it's A, then Class A specific values need to be printed at the end
        //If it's B, then Class B specific values need to be printed at the end
        //If it's C, then Class C specific values need to be printed at the end
        Class clazz;
        switch(userInput) {
        case "A":
            clazz = new A();
            break;
        case "B":
            clazz = new B();
            break;
        case "C":
            clazz = new C();
            break;
        default:
            throw new Exception("Not Implemented");
        }
        System.out.println(clazz.s1);
        System.out.println(clazz.s2);
    }
}

我不想使用以下反射选项，因为它要求用户将变量名称作为参数传递(在下面的示例中为“s1”)，并且它可能不是动态的。

Class aClass = A.class;
Field field = aClass.getField("s1");
System.out.println(field.get(new A()).toString());

我相信应该有其他更好的方法来处理这种情况，但到目前为止我还没有弄清楚。那么有人可以给我一些建议吗？

Answer 1

您可以使用接口(interface)来定义每个类将实现的抽象功能层。

当您创建实现该接口(interface)的类的实例时，您可以确保该类支持该接口(interface)中定义的所需功能子集。

就您而言:

interface MyInterface { // Name this something sensible
    public String getS1();
    public String getS2();
}

public class A implements MyInterface {
    public String getS1() {
      return "a1";
    }
    public String getS2() {
      return "a2";
    }
}

public class B implements MyInterface {
    public String getS1() {
      return "b1";
    }
    public String getS2() {
      return "b2";
    }
}

稍后在代码中使用时:

...
MyInterface clazz; // Please rename this to something more appropriate
switch(userInput) {
    case "A":
        clazz = new A();
        break;
    case "B":
        clazz = new B();
        break;
    case "C":
        clazz = new C();
        break;
    default:
        throw new Exception("Not Implemented");
}
System.out.println(clazz.getS1());
System.out.println(clazz.getS2());