封装Integer.parseInt()的好方法

问题描述

我有一个项目，我们经常使用 Integer.parseInt() 将 String 转换为 int.当出现问题时(例如，String 不是数字而是字母 a 或其他)，此方法将抛出异常.但是，如果我必须在我的代码中到处处理异常，这很快就会变得非常难看.我想把它放在一个方法中，但是，我不知道如何返回一个干净的值来表明转换出错了.

I have a project in which we often use Integer.parseInt() to convert a String to an int. When something goes wrong (for example, the String is not a number but the letter a, or whatever) this method will throw an exception. However, if I have to handle exceptions in my code everywhere, this starts to look very ugly very quickly. I would like to put this in a method, however, I have no clue how to return a clean value in order to show that the conversion went wrong.

在 C++ 中，我可以创建一个方法，该方法接受一个指向 int 的指针，并让该方法本身返回 true 或 false.但是，据我所知，这在 Java 中是不可能的.我还可以创建一个包含真/假变量和转换后的值的对象，但这似乎也不理想.全局值也是如此，这可能会给多线程带来一些麻烦.

In C++ I could have created a method that accepted a pointer to an int and let the method itself return true or false. However, as far as I know, this is not possible in Java. I could also create an object that contains a true/false variable and the converted value, but this does not seem ideal either. The same thing goes for a global value, and this might give me some trouble with multithreading.

那么有没有一种干净的方法来做到这一点?

So is there a clean way to do this?

推荐答案

你可以返回一个 Integer 而不是 int，返回 null解析失败.

You could return an Integer instead of an int, returning null on parse failure.

遗憾的是，Java 没有提供一种在内部不抛出异常的情况下执行此操作的方法 - 您可以隐藏异常(通过捕获它并返回 null)，但如果您这样做，它仍然可能是一个性能问题重新解析数十万位用户提供的数据.

It's a shame Java doesn't provide a way of doing this without there being an exception thrown internally though - you can hide the exception (by catching it and returning null), but it could still be a performance issue if you're parsing hundreds of thousands of bits of user-provided data.

这种方法的代码:

public static Integer tryParse(String text) {
  try {
    return Integer.parseInt(text);
  } catch (NumberFormatException e) {
    return null;
  }
}

请注意，如果 text 为空，我不确定这会做什么.您应该考虑-如果它代表一个错误(即您的代码很可能传递无效值，但不应传递空值)，则抛出异常是合适的；如果它不代表错误，那么您可能应该像处理任何其他无效值一样返回 null.

Note that I'm not sure off the top of my head what this will do if text is null. You should consider that - if it represents a bug (i.e. your code may well pass an invalid value, but should never pass null) then throwing an exception is appropriate; if it doesn't represent a bug then you should probably just return null as you would for any other invalid value.

最初这个答案使用了 new Integer(String) 构造函数；它现在使用 Integer.parseInt 和一个装箱操作；通过这种方式，小值最终会被装箱到缓存的 Integer 对象中，从而在这些情况下更加高效.

Originally this answer used the new Integer(String) constructor; it now uses Integer.parseInt and a boxing operation; in this way small values will end up being boxed to cached Integer objects, making it more efficient in those situations.

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