Skip to content

Regex with negatives lookahead and lookbehind

"Looking different directions" by Paul Kline at (
“Looking different directions” by Paul Kline.

Problem: Match strings that contains a single quotation mark ('), but not multiple ones together.



This is a regex for a single quotation mark with a (?<!') in the left and a (?!’) in the right. The (?<!') is a ?< look behind if not ! a single quotation mark '. The (?!') is a look ahead ? if not ! a single quotation mark '.

Java code:

[java]import java.util.regex.Pattern;

public class RegexProblem {
public static void main(String args[]) {
Pattern single_quote = Pattern.compile("(?<!’)'(?!’)");
String[] phrases = {
for(String phrase: phrases){
System.out.println(String.format("For %s is %s.", phrase,

The output is:

For  is false.
For ' is true.
For a'a is true.
For aaa is false.
For aa'aa is true.
For aa''aa is false.
For aa'''aaa is false.
For aaa''''aaa is false.
Published inenglish

Be First to Comment

Leave a Reply

Your email address will not be published. Required fields are marked *