How To Count Occurrences Of A Grapheme Inward String - Coffee Programming Do Example

Write a programme to count the seat out of occurrences of a graphic symbol inwards String is ane of the mutual programming interview questions non only inwards Java but every bit good inwards other programming languages similar C or C++.  As String inwards a real pop topic on programming interviews together with at that spot are lot of practiced programming exercise on String similar "count seat out of vowels or consonants inwards String", "count seat out of characters inwards String" , How to contrary String inwards Java using recursion or without using StringBuffer etc, it becomes extremely of import to stimulate got venture noesis of String in Java or whatever other programming language. Though, this inquiry is by together with large used to examination candidate's coding mightiness i.e. whether he tin give the sack convert logic to code or not.

In Interview, almost of the fourth dimension Interviewer volition inquire you lot to write a programme without using whatever API method,  as Java is real rich together with it ever around sort of prissy method to produce the job, But it every bit good of import to know rich Java together with opened upward beginning libraries for writing production character code.

Anyway, inwards this question, nosotros volition come across both API based together with non-API based(except few) ways to count a seat out of occurrences of a graphic symbol inwards String on Java.

Java programme to count occurrences of a graphic symbol inwards String

static method countOccurrenceOf(String, character) which takes a String together with graphic symbol together with returns occurrence of graphic symbol into that String.

After that, nosotros volition come across Apache common StringUtils bird for counting occurrence of a graphic symbol inwards String. Apache common StringUtils render countMatches() method which tin give the sack locomote used to count the occurrence of ane graphic symbol or substring.

Finally, nosotros volition come across the almost uncomplicated means of counting graphic symbol using measure for loop together with Java five enhanced for loop. This solution tin give the sack locomote extended non only to finding the occurrence of graphic symbol but every bit good finding occurrences of a substring.

Btw, if you lot are solving this inquiry every bit component division of your Java interview preparation, you lot tin give the sack every bit good depository fiscal establishment represent Cracking the Coding Interview, a collection of 189 programming questions together with solutions from diverse programming undertaking interviews. Your perfect companion for developing coding feel required solving these kinds of problems on interviews. 

Now, let's come across the Java programme to count seat out of occurrence of whatever graphic symbol on String:

import org.springframework.util.StringUtils;

/**
 * Java programme to count the seat out of occurrence of whatever graphic symbol on String.
 * @author Javin Paul
 */
public class CountCharacters {

    public static void main(String args[]) {
         
        String input = "Today is Monday"; //count seat out of "a" on this String.
     
        //Using Spring framework StringUtils bird for finding occurrence of around other String
        int count = StringUtils.countOccurrencesOf(input, "a");
     
        System.out.println("count of occurrence of graphic symbol 'a' on String: " +

                " Today is Monday' using Spring StringUtils " + count);

     
        //Using Apache common lang StringUtils class
        int seat out = org.apache.commons.lang.StringUtils.countMatches(input, "a");
        System.out.println("count of graphic symbol 'a' on String: 'Today is Monday' using common StringUtils " + number);
     
        //counting occurrence of graphic symbol amongst loop
        int charCount = 0;
        for(int i =0 ; i<input.length(); i++){
            if(input.charAt(i) == 'a'){
                charCount++;
            }
        }
        System.out.println("count of graphic symbol 'a' on String: 'Today is Monday' using for loop  " + charCount);
     
        //a to a greater extent than elegant means of counting occurrence of graphic symbol inwards String using foreach loop
     
        charCount = 0; //resetting graphic symbol count
        for(char ch: input.toCharArray()){
            if(ch == 'a'){
                charCount++;
            }
        }    
        System.out.println("count of graphic symbol 'a' on String: 'Today is Monday' using for each loop  " + charCount);
    }
 
       
}

Output
count of occurrence of graphic symbol 'a' on String: 'Today is Monday' using Spring StringUtils 2
count of graphic symbol 'a' on String: 'Today is Monday' using common StringUtils 2
count of graphic symbol 'a' on String: 'Today is Monday' using for loop  2
count of graphic symbol 'a' on String: 'Today is Monday' using for each loop  2

Well, the beauty of this questions is that Interviewer tin give the sack twist it on many ways, they tin give the sack inquire you lot to write a recursive business office to count occurrences of a item character or they tin give the sack fifty-fifty inquire to count how many times each graphic symbol has appeared.

So if a String contains multiple characters together with you lot demand to shop count of each character, regard using HashMap for storing graphic symbol every bit fundamental together with seat out of occurrence every bit value. Though at that spot are other ways of doing it every bit good but I similar the HashMap means of counting graphic symbol for simplicity.

Further Learning
The Coding Interview Bootcamp: Algorithms + Data Structures
Data Structures together with Algorithms: Deep Dive Using Java
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