OK, so I am trying to split a String by ", " which are not inside '[' or ']'. I have a working RegEx for JavaScript but have been unable to convert it to Java syntax.
JS RegEX:
/,(?![^[]*])/g
Example sentence:
ex1 , [ex2 , ex3 ] , ex 4 , ex 4, [ex , ex ]
It works fine on http://refiddle.com but when I try and use the RegEx in Java (under Eclipse) I get an error saying:
Unclosed character class near index 10 ,(?![^[]*])
All I did was remove the '/' at the beginning and the "/g" at the end and I have been unable to translate the Syntax.
What would be the best way to achieve this?
Update for nested square bracket support
Since you need to also support nested square brackets, and the comma should be ignored inside the square brackets, you need a simple parser to collect the chunks of text you need.
public static List<String> splitWithCommaOutsideBrackets(String input) { int BracketCount = 0; int start = 0; List<String> result = new ArrayList<>(); for(int i=0; i<input.length(); i++) { switch(input.charAt(i)) { case ',': if(BracketCount == 0) { result.add(input.substring(start, i).trim());// Trims the item! start = i+1; } break; case '[': BracketCount++; break; case ']': BracketCount--; if(BracketCount < 0) return result; // The BracketCount shows the [ and ] number is unbalanced break; } } if (BracketCount > 0) return result; // Missing closing ] result.add(input.substring(start).trim()); // Trims the item! return result; }
And use it as
String s = "ex1 , [ex2 , ex3 ] , [ hh3 , rt5 , w3 [ bn7 ] ] , ex 4 , ex 4, [ex , ex ]"; List<String> res = splitWithCommaOutsideBrackets(s); for (String t: res) { System.out.println(t); }
Output of the sample Java code:
ex1 [ex2 , ex3 ] [ hh3 , rt5 , w3 [ bn7 ] ] ex 4 ex 4 [ex , ex ]
Note that trimming items is not necessary.
Also, where I return result, you may want to add code throwing an exception rather than returning the result as it is at that moment.
Original answer
In Java character classes, ] and [ must be escaped, unlike in JavaScript where you only have to escape ] symbol (inside the character class).
String pat = ",(?![^\\[]*])"; ^^
Here is an IDEONE demo:
String s = "ex1 , [ex2 , ex3 ] , ex 4 , ex 4, [ex , ex ]"; String pat = ",(?![^\\[]*])"; String[] result = s.split(pat); System.out.println(Arrays.toString(result));
Note that neither in Java, nor in JS, the ], outside the character class, does not have to be escaped.
