问题描述

我有一个学校作业，其中一项任务是解释许多微小的计算，并解释为什么 java 给你它给你的输出..

I have an assignment for school, and one of the tasks is to explain a lot of tiny calculations and explaining why java gives you the output it gives you..

其中一项计算是:

1 + '2' + 3

1 + '2' + 3

这对我来说是一个词汇错误，因为老师为我的系统使用了错误的撇号"，但我已经和其他同学交谈过，他们告诉我他们得到了一个实际的输出，所以我开始阅读它，并发现它应该表示一个 char 变量，并且我还发现了系统特定类型，所以我更改了符号以适用于我的系统，现在我得到了答案 54..

which for me gives a lexical error, as the teacher used the wrong "apostrophes" for my system, but I've talked to other fellow students and they told me they got an actual output, so I started reading about it, and found out that it is supposed to signify a char variable, and I also found out about the system specific types, so I changed the signs to work for my system, and now I get the answer 54..

我看不到其中的逻辑，我尝试用 char 变量在 Google 上添加/计算/数学，但没有找到任何可以很好地解释它的东西..

and I cannot see the logic in it, and I've tried to google adding/calculating/math with char variables, and have found nothing that explains it well..

所以我求助于编码人员，有一天我可能会成为其中的一员，以帮助我理解其中的逻辑..

So I turn to you, the people of coding, that I one day might be a part of to help me understand the logic of this..

这开始是一个家庭作业，我可能只是回答它给出了一个词法错误，因为我的编译器不理解这个符号，但现在它已经达到了我的好奇心，我真的很想知道如何java设法得到这个答案..

this started out as a homework assignment that I probably could have gotten through by just answering that it gives a lexical error because my compiler doesn't understand the symbol, but now it's peaked my curiosity, and I really want to know how java manages to get this answer..

感谢您对此事的任何帮助！:)

thank you for any help on the matter! :)

我可以看到我无法制作作业"标签，所以我希望我可以把它放在这里:)

I can see that I couldn't make a 'homework' tag, so I hope it's okay that I put it here :)

推荐答案

在 Java 中，chars 可以通过 UTF-16 直接映射到 ints.但是，对于大多数常见字符，将 char 值转换为 int 会在 ascii 表中生成它的索引.+ 不是对字符的操作，而是对整数的操作.因此，java 采用 2 并在思考我无法添加这个"之后，意识到如果将其强制转换为 int，它可以添加它.

In Java, chars have a direct mapping to ints by UTF-16. For most common characters, though, casting a char value to an int yields its index on the ascii table. + isn't an operation on chars, but it is an operation for ints. Therefore, java is taking the 2 and after thinking "I can't add this", realizes it can add it if it casts it to an int.

正如您在表中看到的，2"的索引为 50，因此 1 + 50 + 3 = 54.

As you can see in the table, '2' has a index of 50, thus 1 + 50 + 3 = 54.

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