如何检查Java中的变量类型？ [英] How to check type of variable in Java?

问题描述

我如何检查以确保我的变量是int，array，double等......？

How can I check to make sure my variable is an int, array, double, etc...?

编辑：例如，如何检查变量是否为数组？是否有一些函数可以执行此操作？

For example, how can I check that a variable is an array? Is there some function to do this?

推荐答案

Java是一种静态类型语言，因此编译器会为您进行大部分检查。一旦将变量声明为某种类型，编译器将确保只为该类型赋值（或者是该类型的子类型的值）。

Java is a statically typed language, so the compiler does most of this checking for you. Once you declare a variable to be a certain type, the compiler will ensure that it is only ever assigned values of that type (or values that are sub-types of that type).

您给出的示例（int，array，double）这些都是基元，并且没有它们的子类型。因此，如果您将变量声明为 int ：

The examples you gave (int, array, double) these are all primitives, and there are no sub-types of them. Thus, if you declare a variable to be an int:

int x;

您可以确定它只会持有 int values。

You can be sure it will only ever hold int values.

但是，如果您将变量声明为 List ，则变量可能是将保存 List 的子类型。这些示例包括 ArrayList ， LinkedList 等。

If you declared a variable to be a List, however, it is possible that the variable will hold sub-types of List. Examples of these include ArrayList, LinkedList, etc.

如果你确实有 List 变量，并且你需要知道它是否是 ArrayList ，你可以这样做以下：

If you did have a List variable, and you needed to know if it was an ArrayList, you could do the following:

List y;
...
if (y instanceof ArrayList) { 
  ...its and ArrayList...
}

但是，如果您发现自己认为需要这样做，您可能需要重新思考自己的方法。在大多数情况下，如果您遵循面向对象的主体，则不需要执行此操作。当然，每条规则都有例外情况。

However, if you find yourself thinking you need to do that, you may want to re-think your approach. In most cases, if you follow object-oriented principals, you will not need to do this. There are, of course, exceptions to every rule, though.

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