Count the number of occurrences of a specific character in a string

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[edit] Implementations

[edit] C++

#include <algorithm>
#include <string>
using namespace std;
int main() {
        string str("Count, the number,, of commas.");
        int count = count(str.begin(), str.end(), ',');
}

[edit] D

import std.string: count;
void main() {
    string s = "Count, the number,, of commas.";
    auto numberOfCommas = s.count(",");
}

[edit] JavaScript

//create this function
String.prototype.count=function(s1) { 
	return (this.length - this.replace(new RegExp(s1,"g"), '').length) / s1.length;
}

// use like this 
test = "this, as you see, is a sentence, containing many ','s";
numberOfCommas = test.count(','); //4
// or 
numberOfSblank = test.count('s '); //2

// Thanks to code below, above does job better
// This also finds number of any number of strings
// hasan at f p m 3 dot c o m

I think above code seems easier to implement than below. Hasan Cosgun

First, create a new function called replaceAll: 

        String.prototype.replaceAll=function(s1, s2) { 
	  return this.replace(new RegExp(s1,"g"), s2);
	}

Then you can use this function to count the occurrence of a specific character or string within another string. For example, this code counts the number of commas within a string. To count a different character, replace the comma in '[^,]' to another character, such as a lowercase x ('[^x]'). 

        numberOfCommas = text.replaceAll('[^,]','').length + 1;

Another way to do it without RegExp: 

String.prototype.count = function(char){
    return this.split(char).length-1;
}

[edit] Java

There are multiple solutions. For such a low level task you should probably do a performance test to see which method is faster. For instance, regular expressions are very slow in java.

This code will count the number of commas in a string. 


String s = "Count, the number,, of commas.";
int numberOfCommas = s.replaceAll("[^,]","").length();


Also we can do like below: 


public int count(String input, String countString){
        return input.split("\\Q"+countString+"\\E", -1).length - 1;
}

Another solution is: 


public int count(String sourceString, char lookFor) {
        if (sourceString == null) {
                return -1;
        }
        int count = 0;
        for (int i = 0; i < sourceString.length(); i++) {
                final char c = sourceString.charAt(i);
                if (c == lookFor) {
                        count++;
                }
        }
        return count;
}

[edit] Perl


$count = () = $string =~ /colou?r/g; # count the number of  colours (and colors).

[edit] Python

This code will count the number of commas in a string. 


s = "Count, the number,, of commas."
print s.count(",")


[edit] PHP

PHP has a built-in function for this.

see http://php.net/substr_count

substr_count ( string $haystack , string $needle [, int $offset=0 [, int $length ]] ) Returns: INT 


<?php
$text = 'This is a test';
echo strlen($text); // 14

echo substr_count($text, 'is'); // 2

// the string is reduced to 's is a test', so it prints 1
echo substr_count($text, 'is', 3);

// the text is reduced to 's i', so it prints 0
echo substr_count($text, 'is', 3, 3);

// generates a warning because 5+10 > 14
echo substr_count($text, 'is', 5, 10);


// prints only 1, because it doesn't count overlapped subtrings
$text2 = 'gcdgcdgcd';
echo substr_count($text2, 'gcdgcd');
?>

[edit] Ruby


s = "Count, the number,, of commas."
puts s.count(",")

[edit] Zsh

count() {
	local string char
	string="Count, the number,, of commas."
	char=${string//[^,]/}
	print ${(c)#char}	
}
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