无法检查int是否为空 [英] Can't check if int is null

问题描述

我正在尝试使用字典。每当我想检查字典中是否存在元素时，我都这样做：

  int value = results.get（ aKeyThatMayOrMayNotBePresent）; 
 
 if（value！= null）
 // ... 
  

但是编译器说我无法将 int 与< nulltype> 进行比较。在这种情况下，检查 null 的正确方法是什么？

解决方案

您将原始值（int）与null进行比较。由于原语不能为null，因此在这种情况下，应使用相应的对象，例如Integer。所以，你应该写

 整数值= results.get（aKeyThatMayOrMayNotBePresent）; 
  

I'm trying to use a dictionary. Whenever I want to check if an element is present in the dictionary, I do this:

int value = results.get("aKeyThatMayOrMayNotBePresent");

if (value != null)
  // ...

But then the compiler says I can't compare an int to a <nulltype>. What's the correct way to check for null in this case?

解决方案

You're comparing a primitive value (int) to null. Since primitives cannot be null, you should use a corresponding object, such as Integer in this case. So, you should write

Integer value = results.get("aKeyThatMayOrMayNotBePresent");

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