Java 为什么我不能初始化 Map<int, String>？
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Why can't I initialize a Map<int, String>?
提问by Thomas
I want to store a set of int/Stringvalues, but the ints are not necessarily incremental, meaning the data can be:
我想存储一组int/String值，但ints 不一定是增量的，这意味着数据可以是：
<1, "first">, <3, "second">, <9, "third">.
So I'm trying to create the c# equivalent of a Dictionary<int, string>but it just fails to compile, saying "Syntax error on token "int", Dimensions expected after this token" on the line:
因此，我正在尝试创建与 a 等效的 c#，Dictionary<int, string>但它只是无法编译，并在行中说“令牌“int”上的语法错误，此令牌后预期的尺寸”：
private Map<int, String> courses;
Can anyone please tell me why this is? And a good alternative to creating an object as a placeholder for the intand String, then using an array to store them?
谁能告诉我这是为什么？还是创建一个对象作为intand的占位符String，然后使用数组来存储它们的好方法？
采纳答案by Sotirios Delimanolis
You cannot use primitive types as generic type arguments.
您不能将原始类型用作泛型类型参数。
Use
用
private Map<Integer, String> courses;
See more restrictions on Generics here.
在此处查看有关泛型的更多限制。
Dev's contribution: the JLS specifiesthat only reference types (and wildcards) can be used as generic type arguments.
Dev 的贡献：JLS 规定只有引用类型（和通配符）可以用作泛型类型参数。
