How Can I Split Comma-Separated Text While Preserving Quotes?

Splitting Text Using Commas while Preserving Quotes

When parsing comma-separated text, it's important to handle situations where commas appear within quoted substrings, such as this example:

123,test,444,"don't split, this",more test,1

Splitting this string on commas using the default String.split(",") method yields:

123
test
444
"don't split
 this"
more test
1

As you can see, the comma within the "don't split, this" quote is incorrectly interpreted as a separator.

To address this issue, a more sophisticated approach is required. In this case, we can use a regular expression to split the string on commas that are not followed by an even number of double quotes. This ensures that commas inside quoted substrings are not mistaken for separators.

str.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)");

This regular expression uses the following logic:

• (?=): Look-ahead assertion that ensures:

  • (?:[^"]*"[^"]*")*: Matches any number of substrings enclosed in double quotes.
  • [^"]*: Matches any number of non-quote characters.
  • $: End-of-string assertion.

In other words, this look-ahead checks if the current comma is followed by an even number of double quotes and the end of the string. If that's the case, it indicates that the comma is not inside a quoted substring and can be considered a separator. Otherwise, the comma is ignored.

You can also use a simplified version of the regular expression:

str.split("(?x)  ,  (?=  (?:  [^\"]*  \"  [^\"]*  \"  )*  [^\"]*  $  )");

In this version, the modifier (?x) is used to enhance the readability of the regular expression by ignoring whitespace characters.

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