Integer.parseInt（）的好方法 [英] Good way to encapsulate Integer.parseInt()

问题描述

我有一个项目，我们经常使用 Integer.parseInt（）将String转换为int。当某些事情出错（例如， String 不是一个数字，而是字母 a 或其他方式）会抛出异常。但是，如果我必须处理我的代码中的异常，这很快就开始看起来很丑陋。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，以显示转换出错了。

在C ++中，我可以创建一个接受int指针的方法，让方法本身返回true或false。但是，据我所知，这在Java中是不可能的。我也可以创建一个包含true / false变量和转换值的对象，但这似乎也不是理想的。同样的事情也是一个全球性的价值，这可能会给我一些麻烦的多线程。

这样做有一个干净的方法吗？

解决方案

您可以返回一个整数而不是 int ，在解析失败时返回 null 。

这是一个可耻的Java不提供一种这样做的方法，而不会在内部抛出异常 - 你可以隐藏异常（通过捕获它并返回null），但是如果你正在解析数十万位的用户提供的数据。

编辑：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，我不确定如果 text 为空，我的头会做什么。你应该考虑 - 如果它代表一个错误（即你的代码可能会传递一个无效的值，但绝对不能通过null），则抛出一个异常是适当的;如果它不代表一个错误，那么你应该可以像任何其他无效值一样返回null。

最初这个答案使用了 new Integer（String）构造函数;它现在使用 Integer.parseInt 和一个拳击操作;以这种方式，小值将最终被加载到缓存的整数对象中，使其在这些情况下更有效。

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.

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.

So is there a clean way to do this?

解决方案

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

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.

EDIT: Code for such a method:

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

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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