In Set 1, we have discussed general approach for counting the patterns of the form 1(0+)1 where (0+) represents any non-empty consecutive sequence of 0’s.In this post, we will discuss regular expression approach to count the same.

**Examples:**

Input : 1101001 Output : 2 Input : 100001abc101 Output : 2

Below is one of the regular expression for above pattern

10+1

Hence, whenever we found a match, we increase counter for counting the pattern.As last character of a match will always ‘1’, we have to again start searching from that index.

`//Java program to count the patterns ` `// of the form 1(0+)1 using Regex ` ` ` `import` `java.util.regex.Matcher; ` `import` `java.util.regex.Pattern; ` ` ` `class` `GFG ` `{ ` ` ` `static` `int` `patternCount(String str) ` ` ` `{ ` ` ` `// regular expression for the pattern ` ` ` `String regex = ` `"10+1"` `; ` ` ` ` ` `// compiling regex ` ` ` `Pattern p = Pattern.compile(regex); ` ` ` ` ` `// Matcher object ` ` ` `Matcher m = p.matcher(str); ` ` ` ` ` `// counter ` ` ` `int` `counter = ` `0` `; ` ` ` ` ` `// whenever match found ` ` ` `// increment counter ` ` ` `while` `(m.find()) ` ` ` `{ ` ` ` `// As last character of current match ` ` ` `// is always one, starting match from that index ` ` ` `m.region(m.end()-` `1` `, str.length()); ` ` ` ` ` `counter++; ` ` ` `} ` ` ` ` ` `return` `counter; ` ` ` `} ` ` ` ` ` `// Driver Method ` ` ` `public` `static` `void` `main (String[] args) ` ` ` `{ ` ` ` `String str = ` `"1001ab010abc01001"` `; ` ` ` `System.out.println(patternCount(str)); ` ` ` `} ` `} ` |

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Output:

2

**Related Articles :**

- Regular Expression Java
- Quantifiers
- Extracting each word from a String using Regex
- Check if a given string is a valid number (Integer or Floating Point)
- Print first letter of each word in a string using regex

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