String Interview Question: Count the occurrences of a character in a String

In this video, I have explained how to get the count the occurrences of a character in the given String
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[@akhileshhalkarni8192]

Even though the solution might appear complex but using regex is one of the efficient ways to solve these kind of problems
Once you get the syntax, validation of IP addresses, emails and websites becomes possible
My solution :-
import java.util.regex.*;
import java.util.Scanner;
class First {
public static void main(String[] args) {

Scanner scan = new Scanner(System.in);

System.out.println("Enter the String : ");
String input = scan.nextLine();

System.out.println("Enter the character you want to count the occurrence of : ");

//Reading the character
char ch = scan.next().charAt(0);

//Casting from character to string
String regex = Character.toString(ch);

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);

int count = 0;
while(matcher.find())
count++;

System.out.println("The number of occurrences of character '" + regex + "' is " + count);
}
}

[@Ravikumar-gj6qw]

Hi Naveen ,Thanks for refering below jdk 8 videos link as i am learning on how to code on java 8

[@akashrevanna5327]

Clean explaination 👍

[@udaybenake206]

Hi Naveen... When you entered samll 'i' then it has not counted uppercase 'I' any reason or solution for this

[@sasidharreddy5975]

Hi Naveen
For selenium are youtube videos enough ?
Or its needed to buy paid course of you

[@manjunathuma2623]

Any magicial power to write a program to transfer knowledge from "Naveen AutomationLabs" to "me".

[@artimandale8286]

Awesome 👌

[@maheswarani5485]

Vera Level

[@sweetthirty2]

Sir how to print "I love java" into "java love I" plzzz make a video on this frequently getting this problem

[@SharonRueben]

Hello Naveen..Are there any videos on streams. As a beginner I would like to start streams from beginning

[@naveenautomationlabs]

Yes please refer this full series. th-cam.com/play/PLFGoYjJG_fqqHMYWY-rW554LdNKl_jAIj.html

[@Piotr_G112]

What do you think about this solution?
String searchedCharacter="a";
String inputString1="I love Javaa";
List lettersInaList = new ArrayList(Arrays.asList(inputString1.split("")));
int numberOfOccurrences = Collections.frequency(lettersInaList,searchedCharacter);
System.out.println("A letter "+searchedCharacter+ " occurs "+numberOfOccurrences+" times in a text: " +inputString1+".");

[@FactGuru2108]

How will we print occurrence of all character in one go rather then checking each character occurrence from main method? i.e.
I -->2
O-->1
t--->2
e--->1

[@f.a5148]

i have the same question

[@jyotidarekar8006]

public static void main(String[] args) {
String str = "String Buffer ClaSs";
String str1 = str.replaceAll(" ", "").toLowerCase();
System.out.println(str1);

Map map = new HashMap();

char[] arr=str1.toCharArray();

for(int i = 0; i

[@Shradha6979]

Each and every word count in a given string....

[@DaveRegan]

var NumberOfOccurences = "this is a test".Count(c=>c=='i');

[@pavankumar-xb7nw]

Actually in interview they asked me to print each character with count in string. And that time we need to pass only String and not matching character. How to make it?

[@ashwiniv7053]

import java.util.*;
class Main {
public static void main(String[] args) {
String str= "aabbbcc";
getCharCount(str);
}
public static void getCharCount(String str){
Map map = new HashMap();
for(char ch: str.toCharArray()){
if(map.containsKey(ch)){
map.put(ch, map.get(ch)+1);
}
else
map.put(ch,1);
}
System.out.println(map); // to print character with count of occurance
// to print only the count and not the
}
}

[@gurunadhmitikela2918]

@@ashwiniv7053 Thank you 🙏. I tried this working fine. but are you getting the output in order of characters?

[@gopinathm.p1924]

@@gurunadhmitikela2918 in hash map , the order won't be maintained.

[@ashwiniv7053]

@@gurunadhmitikela2918 if you want the output in order the sort it first. I hope I answered your question

[@DaveRegan]

var NumberOfOccurences = "This is a test string".GroupBy(c=>c).OrderBy(c=>c.Key.ToString()).ToList();
NumberOfOccurences.ForEach(c => Console.WriteLine("'"c.Key + "' " + c.Count()));

[@crazyabchackerakatechanima4098]

Can u make part 5 of star patterns 😀

[@naveenautomationlabs]

Sure, more patterns are coming soon

[@crazyabchackerakatechanima4098]

@@naveenautomationlabs :D

[@shaikasifhussain6730]

like same interview Question
want to reverse only one word in a sentence?
Ex: input: "Naveen Automation Labs"
Output: "Naveen noitamotuA Labs"

[@naveenautomationlabs]

Which word? Middle one? Or second one?

[@shaikasifhussain6730]

@@naveenautomationlabs thanks for reply 😊
middle one!

[@ShinAkuma]

Try doing it yourself instead of asing for code.
I'll give you a logic. Implement it yourself.
Take your sentence and break it into a String array using Space as the delimiter.
Iterate over this array and pick every word and pass it through a reverse function and concatenate all words of the array using space.
The reverse function is simple, if you dont want to use the StringBuffer reverse, just break your word into a array of character then swap the first character with last character and move inwards from there.
Now you dont mention by what logic we are picking the words here, you figure that out yourself according to your requirements.

[@shaikasifhussain6730]

@@ShinAkuma yes by using split concept

[@shasankkumar7246]

@@shaikasifhussain6730 this is one solution :
// Helper reverse function
public static void rev(char[] str, int start, int end) {
while(start < end) {
char temp = str[start];
str[start] = str[end];
str[end] = temp;
start++;
end--;
}
}
//Main function
public static void revWord(String str, String word) {
if(str.isEmpty()|| word.isEmpty()|| str.length() < word.length()) {
System.out.println("Invalid Input Error");
return;
}
int start = str.indexOf(word);
int end = start + word.length() - 1;
char[] strArray = str.toCharArray();
rev(strArray,start,end);
for(char ch : strArray) {
System.out.print(ch);
}
}
public static void main (String[] args) {
String main = "HelloWorldHello";
String word = "World";
revWord(main,word);
}
Hope it helped!
test different scenarios of strings and let me know if there is any fault, I'd like to correct Thank You!!

[@vinith2320]

This is also an easiest way to count occurrences of each character Naveen
class string
{
public static void main(String[]args)
{
String s="Naveen Automation Labs";
s=s.toLowerCase();
for(char ch='a';ch

[@kumarrdy5420]

No.

[@vinith2320]

@@kumarrdy5420 No means ... ?

[@ShinAkuma]

@@vinith2320 This is not a good way to do it. Don't use nested loops. You're doing it in O(n^2) time, while it can be done in O(n)

[@ShinAkuma]

public class Test
{
public static void main(String[] args) throws IOException
{
String s = "Naveen Automation Labs";
s = s.toUpperCase();
s = s.replaceAll(" ", "");
int chr[] = new int[26];

for(int i=0; i

[@vinith2320]

@@ShinAkuma Thank you for your feedback 😊