How to Split Strings with Spaces Inside Quotes Using Regular Expressions?

Regex for Splitting Strings: Ignoring Spaces Within Quotes

Identifying spaces for string splitting can be challenging when those spaces are enclosed within single or double quotes. To address this, consider the following regular expression:

[^\s"']+|\"([^\"]*)"|'([^']*)'

This expression separates the string into two types of patterns:

• Unquoted words: Any sequence of characters not containing spaces or quotes, captured in the first group.
• Quoted strings: Sequences enclosed in single or double quotes, with no quotes within them. The capturing groups capture the text within the quotes, excluding the quotes themselves.

Java Implementation:

The following Java code uses this regular expression to split the string:

List<String> matchList = new ArrayList<>();
Pattern regex = Pattern.compile("[^\s\"']+|\"([^\"]*)"|'([^']*)'");
Matcher regexMatcher = regex.matcher(subjectString);
while (regexMatcher.find()) {
    if (regexMatcher.group(1) != null) {
        matchList.add(regexMatcher.group(1)); // Double-quoted string
    } else if (regexMatcher.group(2) != null) {
        matchList.add(regexMatcher.group(2)); // Single-quoted string
    } else {
        matchList.add(regexMatcher.group()); // Unquoted word
    }
}

Simpler Option:

If maintaining quotes in the returned list is acceptable, a simpler version of the code is possible:

List<String> matchList = new ArrayList<>();
Pattern regex = Pattern.compile("[^\s\"']+|\"[^\"]*\"|'[^']*'");
Matcher regexMatcher = regex.matcher(subjectString);
while (regexMatcher.find()) {
    matchList.add(regexMatcher.group());
}

This approach is less complex but includes quotes in the returned list elements.

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