对于Java中的*****类型，方法*****未定义 [英] The method *****is undefined for the type***** in Java

问题描述

我正在尝试从另一个包中的抽象类Sprite调用一个方法，但我得到了方法getSymbol（）未定义Sprite类型

I'm trying to call a method from an abstract class Sprite in another package, but I got "The method getSymbol() is undefined for the type Sprite"

这是代码。

这是来自另一个包精灵的代码

And here is the code from another package sprites

我想问题是那个来自抽象类的方法无法实例化。

I guess the problem is that the method from an abstract class cannot be instantiated.

但我不知道如何修复它。

But I don't know how to fix it.

推荐答案

这就是问题所在：

public class ArrayGrid<Sprite> implements Grid<Sprite>

你宣布上课的方式， Sprite 是类型参数的名称。你已经把它变成了一个通用的类，我怀疑你不是故意的。在该类中， Sprite 是指类型参数，而不是类型 - 因此您可以拥有 ArrayGrid< String> 它实现了 Grid< String> ...此时你有一个字符串数组而不是精灵数组，所以毫无疑问 getSymbol （）不起作用，就像问题的一个症状一样。

The way you've declared the class, Sprite is the name of a type parameter. You've made this a generic class, and I suspect you didn't mean to. Within that class, Sprite refers to the type parameter, not the type - so you could have an ArrayGrid<String> which implemented Grid<String>... at which point you'd have a string array rather than a sprite array, so it's no wonder that getSymbol() wouldn't work, just as one symptom of the problem.

我怀疑你只是想要：

public class ArrayGrid implements Grid<Sprite>

此时，精灵真的是指类型。这意味着你可以避免代码无法解决数组，而只需写：

At that point, Sprite really refers to the type. And that means you can avoid the code that wouldn't work around arrays, and instead just write:

this.grid = new Sprite[numRows][numColumns];

然后没有必要禁止警告：）

Then there's no need to suppress the warnings :)

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