How To Count Occurrences Of A Graphic Symbol Inwards String - Coffee Programming Practise Example

Write a plan to count the pose out of occurrences of a grapheme inwards String is 1 of the mutual programming interview questions non simply inwards Java but likewise inwards other programming languages similar C or C++.  As String inwards a really pop theme on programming interviews in addition to at that topographic point are lot of practiced programming exercise on String similar "count pose out of vowels or consonants inwards String", "count pose 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 corporation noesis of String in Java or whatever other programming language. Though, this query is to a greater extent than ofttimes than non used to exam candidate's coding mightiness i.e. whether he tin sack convert logic to code or not.

In Interview, close of the fourth dimension Interviewer volition inquire you lot to write a plan without using whatever API method,  as Java is really rich in addition to it ever approximately variety of overnice method to create the job, But it likewise of import to know rich Java in addition to opened upward rootage libraries for writing production lineament code.

Anyway, inwards this question, nosotros volition come across both API based in addition to non-API based(except few) ways to count a pose out of occurrences of a grapheme inwards String on Java.

Java plan to count occurrences of a grapheme inwards String

static method countOccurrenceOf(String, character) which takes a String in addition to grapheme in addition to returns occurrence of grapheme into that String.

After that, nosotros volition come across Apache park StringUtils degree for counting occurrence of a grapheme inwards String. Apache park StringUtils supply countMatches() method which tin sack live on used to count the occurrence of 1 grapheme or substring.

Finally, nosotros volition come across the close uncomplicated means of counting grapheme using measure for loop in addition to Java five enhanced for loop. This solution tin sack live on extended non simply to finding the occurrence of grapheme but likewise finding occurrences of a substring.

Btw, if you lot are solving this query every bit component of your Java interview preparation, you lot tin sack likewise banking company lucifer Cracking the Coding Interview, a collection of 189 programming questions in addition to 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 plan to count pose out of occurrence of whatever grapheme on String:

import org.springframework.util.StringUtils;

/**
 * Java plan to count the pose out of occurrence of whatever grapheme on String.
 * @author Javin Paul
 */
public class CountCharacters {

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

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

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

Output
count of occurrence of grapheme 'a' on String: 'Today is Monday' using Spring StringUtils 2
count of grapheme 'a' on String: 'Today is Monday' using park StringUtils 2
count of grapheme 'a' on String: 'Today is Monday' using for loop  2
count of grapheme 'a' on String: 'Today is Monday' using for each loop  2

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

So if a String contains multiple characters in addition to you lot demand to shop count of each character, reckon using HashMap for storing grapheme every bit primal in addition to pose out of occurrence every bit value. Though at that topographic point are other ways of doing it every bit good but I similar the HashMap means of counting grapheme for simplicity.

Further Learning
The Coding Interview Bootcamp: Algorithms + Data Structures
Data Structures in addition to Algorithms: Deep Dive Using Java
Write a plan to honour factorial of pose out using recursion

How to impress Fibonacci serial inwards Java

How to banking company lucifer if a pose out is Armstrong pose out inwards Java

How to banking company lucifer prime numbers inwards Java

How to contrary pose out inwards Java without using API method

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