为什么idea提示A "HashMap<Integer, String>" cannot contain a "Byte" in a "Integer" type.

这是因为Java中的HashMap是基于键值对存储数据的，其中键和值都有自己的数据类型。在你的代码中，你定义了一个`HashMap<Integer, String>`，它的键的数据类型是Integer，值的数据类型是String。当你尝试将一个Byte类型的值添加到HashMap中时，由于Byte类型不能转换为Integer类型，所以会出现编译错误。

如果你想要将Byte类型的值添加到HashMap中，你需要将HashMap的键的数据类型改为Byte。例如，你可以这样定义一个HashMap：

HashMap<Byte, String> map = new HashMap<>();

这样就可以将Byte类型的值添加到HashMap中了。

相关问题

Cannot infer type arguments for HashMap<>

`HashMap<>` is a generic class in Java, which means that it requires type arguments to be specified. You need to specify the type of keys and values. For example, if you want a `HashMap` that maps strings to integers, you would declare it as follows:

HashMap<String, Integer> map = new HashMap<String, Integer>();

In this case, `String` is the type of keys, and `Integer` is the type of values. If you want to use type inference, you can omit the type arguments on the right-hand side of the assignment, and Java will infer them from the context:

HashMap<String, Integer> map = new HashMap<>();

Here, Java infers the type arguments based on the left-hand side of the assignment.