如何在Java字符串中的每个“，”之前输入“。”两个空格

Question

I've got a string in my Java project which looks something like this
9201,92710,94500,920,1002

How can I enter a dot 2 places before the comma? So it looks like this:
920.1,9271.0,9450.0,92.0,100.2

I had an attempt at it but I can't get the last number to get a dot.

numbers = numbers.replaceAll("([0-9],)", "\\.$1");

The result I got is
920.1,9271.0,9450.0,92.0,1002

Note: The length of the string is not always the same. It can be longer / shorter.

Answer 1

1. Check if string ends with ",". If not, append a "," to the string, run the same replaceAll, remove "," from end of String.
2. Split string by the "," delimiter, process each piece adding the "." where needed.
3. Just add a "." at numbers.length-1 to solve the issue with the last number

Answer 2

As your problem is not only inserting the dot before every comma , but also before end of string , you just must add this additional condition to your capturing group:

numbers = numbers.replaceAll("([0-9](,|$))", "\\.$1");

As suggested by Siguza, you could as well use a non-capturing group which is even more what a "human" would expect to be captured in the capturing group:

numbers = numbers.replaceAll("([0-9](?:,|$))", "\\.$1");

But as a non-capturing group is (although a really nice feature) not standard Regex and the overhead is not that significant here, I would recommend using the first option.

Answer 3

您可以使用单词边界：

numbers = numbers.replaceAll("(\\d)\b", ".$1");

Answer 4

Your solution is fine, as long as you put a comma at the end like dan said. So instead of:

numbers = numbers.replaceAll("([0-9],)", "\\.$1");

write:

numbers = (numbers+",").replaceAll("([0-9],)", "\\.$1");
numbers = numbers.substring(0,numbers.size()-1);

Answer 5

You may use a positive lookahead to check for the , or end of string right after a digit and a zeroth backreference to the whole match:

String s = "9201,92710,94500,920,1002";
System.out.println(s.replaceAll("\\d(?=,|$)", ".$0"));
// => 920.1,9271.0,9450.0,92.0,100.2

See the Java demo and a regex demo .

Details :

• \\\\d - exactly 1 digit...
• (?=,|$) - that must be before a , or end of string ( $ ).

A capturing variation ( Java demo ):

String s = "9201,92710,94500,920,1002";
System.out.println(s.replaceAll("(\\d)(,|$)", ".$1$2"));

Answer 6

You where right to go for the replaceAll method. But your regex was not matching the end of the string, the last set of numbers.

Here is my take on your problem:

  public static void main(String[] args) {
    String numbers = "9201,92710,94500,920,1002";
    System.out.println(numbers.replaceAll("(\\d,|\\d$)", ".$1"));
  }

the regex (\\\\d,|\\\\d$) matches a digit followed by a comma \\d, , OR | a digit followed by the end of the string \\d$ . I have tested it and found to work.

As others have suggested you could add a comma at the end, run the replace all and then remove it. But it seems as extra effort. Example:

  public static void main(String[] args) {
    String numbers = "9201,92710,94500,920,1002";
    //add on the comma
    numbers += ",";

    numbers = numbers.replaceAll("(\\d,)", "\\.$1");

    //remove the comma
    numbers = numbers.substring(0, numbers.length()-1);
    System.out.println(numbers);
  }