在每第 n 个位置拆分一个字符串 [英] Split a string, at every nth position
问题描述
我使用这个正则表达式在每个第三个位置分割一个字符串:
I use this regex to split a string at every say 3rd position:
String []thisCombo2 = thisCombo.split("(?<=\G...)");
其中 G 后面的 3 个点表示要拆分的每第 n 个位置.在这种情况下，3 个点表示每 3 个位置.一个例子:
where the 3 dots after the G indicates every nth position to split. In this case, the 3 dots indicate every 3 positions. An example:
Input: String st = "123124125134135145234235245"
Output: 123 124 125 134 135 145 234 235 245.
我的问题是，如何让用户控制必须拆分字符串的位置数?换句话说，我如何制作这 3 个点，由用户控制的 n 个点?
My question is, how do i let the user control the number of positions where the string must be split at? In other words, how do I make those 3 dots, n dots controlled by the user?
推荐答案
为了大幅提升性能，另一种方法是在循环中使用 substring():
For a big performance improvement, an alternative would be to use substring() in a loop:
public String[] splitStringEvery(String s, int interval) {
int arrayLength = (int) Math.ceil(((s.length() / (double)interval)));
String[] result = new String[arrayLength];
int j = 0;
int lastIndex = result.length - 1;
for (int i = 0; i < lastIndex; i++) {
result[i] = s.substring(j, j + interval);
j += interval;
} //Add the last bit
result[lastIndex] = s.substring(j);
return result;
}
示例:
Input: String st = "1231241251341351452342352456"
Output: 123 124 125 134 135 145 234 235 245 6.
它不像 stevevls 的解决方案那么短，但它效率更高(请参阅下面)，我认为以后会更容易调整，当然取决于你的情况.
It's not as short as stevevls' solution, but it's way more efficient (see below) and I think it would be easier to adjust in the future, of course depending on your situation.
2,000 个字符的长字符串 - 间隔为 3.
2,000 characters long string - interval is 3.
split("(?<=\G.{" + count + "})") 性能(以毫秒为单位):
split("(?<=\G.{" + count + "})") performance (in miliseconds):
7, 7, 5, 5, 4, 3, 3, 2, 2, 2
splitStringEvery() (substring()) 性能(以毫秒为单位):
splitStringEvery() (substring()) performance (in miliseconds):
2, 0, 0, 0, 0, 1, 0, 1, 0, 0
<小时>
2,000,000 个字符的长字符串 - 间隔为 3.
2,000,000 characters long string - interval is 3.
split() 性能(以毫秒为单位):
split() performance (in miliseconds):
207, 95, 376, 87, 97, 83, 83, 82, 81, 83
splitStringEvery() 性能(以毫秒为单位):
splitStringEvery() performance (in miliseconds):
44, 20, 13, 24, 13, 26, 12, 38, 12, 13
<小时>
2,000,000 个字符的长字符串 - 间隔为 30.
2,000,000 characters long string - interval is 30.
split() 性能(以毫秒为单位):
split() performance (in miliseconds):
103, 61, 41, 55, 43, 44, 49, 47, 47, 45
splitStringEvery() 性能(以毫秒为单位):
splitStringEvery() performance (in miliseconds):
7, 7, 2, 5, 1, 3, 4, 4, 2, 1
<小时>
结论:
splitStringEvery() 方法快得多(即使在 Java 7u6 中的变化)，并且随着间隔变大而升级.
The splitStringEvery() method is a lot faster (even after the changes in Java 7u6), and it escalates when the intervals become higher.
即用型测试代码:
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