Use of greedy quantifier * in java?

Question

Vulpes · Answer

In Java regular expressions, the * quantifier matches the preceding character or group zero or more times. By default it matches the longest sequence of characters which fits the pattern, which is called 'greedy' behavior. However, if you follow it with a ?, it matches the shortest sequence of characters which fits the pattern, which is called 'reluctant' (or 'lazy') behavior. The following example illustrates the difference between the two kinds of behavior: // Regular2.java import java.util.regex.*; class Regular2 { public static void main(String[] args) { String text = "A stitch in time"; // match all characters up to 't' // using greedy quantifier Pattern pat = Pattern.compile(".*t"); Matcher mat = pat.matcher(text); while(mat.find()) { System.out.println(mat.group()); } System.out.println(); // using reluctant quantifier Pattern pat2 = Pattern.compile(".*?t"); Matcher mat2 = pat2.matcher(text); while(mat2.find()) { System.out.println(mat2.group()); } } } The output is: A stitch in t A st it ch in t When * is greedy it matches as many characters as possible until it finds a 't' and hence only finds the single sub-string : A stitch in t However, when it's reluctant, it matches as few characters as possible until it finds a 't' and hence finds the 3 sub-strings above.

Abhijeet Singh · Answer

Thank You sir.. :)