当递增时，我怎么能让数组的索引“翻转”？ [英] How could I have the index of an array 'roll over' when incrementing?

问题描述

所以我有一个长度为4的数组。当我将它递增1并且数字大于数组的长度时，我希望它能翻转。

So I have an Array with a length of 4. When I increment it by 1 and the number gets bigger than the length of the array, I'd like it to rollover.

例如：

current_index = 3;
current_index++;
//current_index is now 0 again

current_index = 3;
current_index += 2;
//current_index would be 1

current_index = 0;
current_index--;
//current_index would be 3

我正在使用if-else来解决它这个

I'm currently solving it with if-else like this

if (current_index == textviewlist.length + 1)
     current_index = 0;
else if (current_index == textviewlist.length + 2)
     current_index = 1;
else if (current_index == -1)
     current_index = 3;

但我觉得这不是一个合适的解决方案或好的代码。

But I feel like this isn't an appropriate solution, or "good" code.

编辑：我尝试了你的建议，但显然java的行为与负数表现奇怪。
当我尝试

Edit: I tried your suggestion, but apparently java behaves strangely with negative numbers. When I try

current_index = (current_index - 1) % textviewlist.length;

Java取索引0，将其减1（ - 1）然后

Java takes the index "0", decreases it by 1 ("-1") and then

 -1 % 4 = -1

我预计它是3，见 Wolfram Alpha：-1 mod 4
但显然java％运算符不同于模运算符？

I expected it to be 3, see Wolfram Alpha: -1 mod 4 But apparently the java % operator is not the same as the modulo operator?

编辑2 ：我在这里找到了一个解决方案：使Java的模数表现得像它应该的最佳方法负数？ - Stack Overflow

Edit 2: I found a solution here: Best way to make Java's modulus behave like it should with negative numbers? - Stack Overflow

我可以这么做：

current_index -= 1;
current_index = (current_index % textviewlist.length + textviewlist.length)  % textviewlist.length;

推荐答案

您可以使用模运算符。

current_index = (current_index + n) % 4;

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