从父类继承方法不起作用

发布于 2024-11-06 05:25:49 字数 508 浏览 6 评论 0原文

我想知道为什么我的子类没有正确继承。

如果我有...

public class ArithmeticOp{

    //some constructor

    public static void printMessage(){
        System.out.println("hello");
    }

}

并且另一个类

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    op.printMessage();           //returns error
}

我的 Eclipse 不断返回“令牌“printMessage”上的语法错误，此令牌后需要标识符”

有人可以帮忙吗？谢谢！还有其他方法可以从父类以及子类调用方法吗？非常感谢！

原文

I was wondering why my child class isn't inheriting correctly.

if i had...

public class ArithmeticOp{

    //some constructor

    public static void printMessage(){
        System.out.println("hello");
    }

}

and another class

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    op.printMessage();           //returns error
}

my eclipse keeps returning "Syntax error on token "printMessage", Identifier expected after this token"

could someone please help? thanks! are there other ways to call methods from the parent class as well from a child class? thanks a bunch!

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小霸王臭丫头 2024-11-13 05:25:49

这是因为您不能将任意代码放入类主体中：

public class AddOp extends ArithmeticOp{

    ArithmeticOp op = new ArithmeticOp(); // this is OK, it's a field declaration
    op.printMessage();                    // this is not OK, it's a statement
}

op.printMessage(); 需要位于方法内部或初始值设定项块内部。

除此之外，你的代码感觉不对。为什么要在它自己的子类之一ArithmeticOp内部实例化一个ArithmeticOp？

This is because you can't put arbitrary code into the class body:

public class AddOp extends ArithmeticOp{

    ArithmeticOp op = new ArithmeticOp(); // this is OK, it's a field declaration
    op.printMessage();                    // this is not OK, it's a statement
}

The op.printMessage(); needs to be inside a method, or inside an initializer block.

That aside, your code feels wrong. Why would you want to instantiate an ArithmeticOp inside one of its own subclasses?

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野生奥特曼 2024-11-13 05:25:49

这是因为该方法被声明为静态。我可能错了，我相信如果我错了，有人会发表评论，但我认为你可以这样做：

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    super.printMessage();           //super should call the static method on the parent class
}

或者

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    ArithmeticOp.printMessage();           //Use the base class name
}

It's because that method is declared as static. I may be mistaken and I'm sure someone will comment if I am but I think you can do:

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    super.printMessage();           //super should call the static method on the parent class
}

public class AddOp extends ArithmeticOp{

    //some constructor

    ArithmeticOp op = new ArithmeticOp();
    ArithmeticOp.printMessage();           //Use the base class name
}

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