CODEWITHSUNDEEP
javastring
Mariano
Mariano

Reputation: 3

How should I count the number of occurrences of a character at the beginning of a string in Java

I have a string similar to this ,,,foo,bar and I need to count the amount of "," at the beginning of the string in java any ideas?

Upvotes: 0

Views: 370

Answers (7)

Michał Šrajer
Michał Šrajer

Reputation: 31182

You can also use regexp:

public static int countCommasAtBegin(String str) {
    Matcher commas = Pattern.compile("^,*").matcher(str);
    if (commas.find()) {
        return commas.group().length();
    } else {
        return 0;
    }
}

but for such trivial task I prefer to use simple loop.

Upvotes: 0

Michał Šrajer
Michał Šrajer

Reputation: 31182

If you don't want to use any any external jars just write a simple function:

public static int countAtBegin(String str, char c) {
    for (int ret = 0; ret < str.length(); ret++) {
        if (str.charAt(ret) != c)
            return ret;
    }
    return str.length();
}

Upvotes: 0

Drupad Panchal
Drupad Panchal

Reputation: 393

This quick-n-dirty solution worked for me.

public static void main(String[] args)
{
    String s = ",,,foo,bar";
    int count = 0;
    for (int i = 0; i < s.length() ; i++) {
        if (s.charAt(i) != ',')
            break;
        count++;
    }

    System.out.println("count " + count);
}

Update: just realized that you only need to count the ',' at the beginning of the string and not the middle. I've updated the code to do that.

Upvotes: 0

harsh
harsh

Reputation: 7692

If starting characters are known then build a regex pattern and get the first group. First group string will contain the exact match of desired sequence, length of this string is the resultant count.

Upvotes: 1

dogbane
dogbane

Reputation: 274612

Take a look at the String javadoc. It contains methods you can use to get the length of the String and get characters at certain positions.

Upvotes: 1

talnicolas
talnicolas

Reputation: 14053

A simple loop (while or for) containing a if with a condition of equality that increments a counter if true should be enough.

Upvotes: 0

tskuzzy
tskuzzy

Reputation: 36456

Have a counter variable which counts the number of occurrences. Then loop through the entire String, using charAt(i) to get the char at position i. Test to see if it's equal to charAt(0). If it is, increment counter and if it isn't, break out of the loop.

Upvotes: 2

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