Java 中类型***** 的方法 ***** 未定义 [英] The method *****is undefined for the type***** in Java

问题描述

我试图从另一个包中的抽象类 Sprite 调用一个方法，但我得到方法 getSymbol() 未定义为 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.

这是另一个包精灵的代码

And here is the code from another package sprites

我猜问题是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.

但我不知道如何解决它.

But I don't know how to fix it.

推荐答案

这是问题所在:

public class ArrayGrid<Sprite> implements Grid<Sprite>

您声明类的方式，Sprite 是类型参数的名称.你已经把它变成了一个通用类，我怀疑你不是故意的.在该类中，Sprite 指的是类型参数，而不是类型 - 所以你可以有一个实现 Grid 的 ArrayGrid>...此时您将拥有一个字符串数组而不是一个精灵数组，所以难怪 getSymbol() 不起作用，就像 one问题的症状.

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，Sprite 真正指的是类型.这意味着您可以避免无法处理数组的代码，而只需编写:

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];

那么就没有必要抑制警告:)

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

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