How to count the number of comparisons in this algorithm?

I’m learning to analyze the performance of an algorithm. Here, I have created an algorithm to count the number of capital letters in a sentence. But I don’t understand how to calculate comparisons in an algorithm. Here is my algorithm:

public class CountCapitalLetters{
    public static void main(String[] args) {
        String str = "Wonderfull World";
        char[] capitalLetters = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
        int count = 0;
        
        for (int i = 0; i < str.length(); i++) {
            for (int j = 0; j < capitalLetters.length; j++) {
                if (capitalLetters[j] == str.charAt(i))
                    count += 1;
            }
        }
    }
}

And this is the pseudocode:

String str = “Wonderfull World”;
Array capitalLetters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
count = 0
n = length of str
nn = length of capitalLetters

for i = 0 to n
    for j = 0 to nn
        if capitalLetters[j] == str[i]
             count += 1;
        endif
    endfor
endfor

Can someone help me?

Answer

The number of comparisons made is the same as the length of characters of the variable str times 26.

Number of comparisons = str.length() * 26

This is because you are comparing each and every character in str to all the capital letters in the array capitalLetters. Note that I said “character” and not letter, so any spaces in str is also included.

Have a look at this program:

public class Test
{
    public static void main(String[] args) 
    {
        String str = "Wonderfull World" ;
        char[] capitalLetters = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'} ;
        
        int capitalLetterCount = 0 ;
        int comparisonCount = 0 ;

        for (int i = 0; i < str.length(); i++) 
        {
            for (int j = 0; j < capitalLetters.length; j++) 
            {
                if(capitalLetters[j] == str.charAt(i))      // if the letter is a capital letter
                    capitalLetterCount += 1;

                comparisonCount+=1 ;        // as a comparison has been made above
            }
        }

        System.out.println("Number of capital letters: " + capitalLetterCount) ;
        System.out.println("Number of capital comparisons made: " + comparisonCount) ;

        int c = str.length() * 26 ;
        System.out.println(c) ;
    }
}

Every time a comparison is made, the variable comparisonCount is incremented by 1. Run the program and see that both the variables comparisonCount and c have the same values.