java 数组索引和增量在同一行
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array index and increment at the same line
提问by godMode
quick basic question, how does android/java handle the following lines of code:
快速基本问题，android/java 如何处理以下代码行：
int[] someArray = new int[5];
int index = 0;
int result;
result = someArray[index++];
which index would be passed on to the result? will it increment the index first then pass it to someArray[1]? or will it pass the original value of index to someArray[0] and then increment the index?
哪个索引会传递给结果？它会先增加索引然后将它传递给 someArray[1] 吗？还是将索引的原始值传递给 someArray[0] 然后增加索引？
回答by andronikus
From http://download.oracle.com/javase/tutorial/java/nutsandbolts/op1.html:
从http://download.oracle.com/javase/tutorial/java/nutsandbolts/op1.html：
The code result++; and ++result; will both end in result being incremented by one. The only difference is that the prefix version (++result) evaluates to the incremented value, whereas the postfix version (result++) evaluates to the original value.
代码结果++；和++结果；都将以结果加一而告终。唯一的区别是前缀版本 (++result) 计算为递增值，而后缀版本 (result++) 计算为原始值。
So you'll get someArray[0].
所以你会得到someArray[0].
回答by derekerdmann
In Java and similar languages, using index++only increment the value after the expression has been evaluated. If you want to increment before using the variable, use ++index.
在 Java 和类似语言中，index++仅在表达式计算后使用递增值。如果您想在使用变量之前递增，请使用++index.
In this case, it will use the original value of indexto obtain result, and then increase its value to 1.
在这种情况下，它将使用 的原始值index来获取result，然后将其值增加到 1。
回答by Gravity
index++returns indexand then increments by 1. So it will do result = someArray[0]and then set indexto 1.
index++返回index然后增加 1。所以它会做result = someArray[0]然后设置index为 1。
In contrast, ++indexwould do the increment and then pass the incremented value. So if you wanted resultset to someArray[1]in the above code, you would use ++index.
相反，++index会做增量然后传递增量值。所以如果你想在上面的代码中result设置为someArray[1]，你可以使用++index.
As someone else said, please don't use this kind of syntax. Instead, please write
正如其他人所说，请不要使用这种语法。相反，请写
index++;
result = someArray[index];
回答by Soufiane Hassou
It will pass someArray[0]and then increment index
它将通过someArray[0]然后递增index
It is not dependent from android, the general rule is:
它不依赖于android，一般规则是：
index++ means evaluates index and then increment it, while ++index is increment then evaluate
index++ 表示对 index 求值然后递增，而 ++index 是递增然后求值
回答by Brandon Langley
1.) Avoid doing this sort of thing, in fact with code I review I ask people to never do this.
1.) 避免做这种事情，事实上，在我的代码中，我要求人们永远不要这样做。
Not specifically using ++, but the fact you're doing it as part of evaluating something else. Generally it won't cost the compiler any extra to have that increment as a separate statement, and putting it inline like that means the next person coming along has to take a second and evaluate the increment themselves.
不是专门使用 ++，而是将它作为评估其他东西的一部分的事实。一般来说，将增量作为单独的语句不会花费编译器任何额外的费用，并且像这样将其内联意味着下一个人必须花一点时间自己评估增量。
I know it's minor, and it's a little nitpicky, but stuff like this costs extra time during code review, it's easy to miss while scanning, etc. And it saves you nothing but a few extra keystrokes, which when compared against code clairity and readability is not worth it IMO.
我知道这很次要，而且有点挑剔，但是像这样的东西在代码期间会花费额外的时间，在扫描时很容易错过等等。而且它只会为您节省一些额外的按键，与代码的清晰度和可读性相比不值得 IMO。
2) You will get someArray[0], and after moving on to the next line, you will have your index incremented.
2) 您将获得 someArray[0]，在移至下一行后，您的索引将增加。
