Occurrence of a character in a string using Java

Hi coders! You have been solving various String related problems some difficult some easy but this time I am here with a different type of problem which some of you people may have already seen or maybe not. Also for this problem, I have come up with an efficient solution using Java which you people will definitely be going to like. The task is to find the occurrence of a character in a string in Java. For example :

If the given string is: “code speedy”, then the output should be like-

Output :

c = 1  

o = 1

d = 2

e = 3

s = 1

p = 1

y = 1

Now to solve this problem there may be various methods which may seem easy to code but personally, I found the efficient approach for this problem which is Hashmap. Hashmap works on {key, value} pair.Using Hashmap one has to traverse the whole string once which reduces the time complexity and obviously, a good programmer always looks for a less complex solution. So following are steps to solve the given problem using Hashmap.

1. First of all declare a Hashmap of {char,int}.
2. Traverse the string and check for the traversed character in Hashmap.
3. Count the frequency of each character.
4. After traversing the string, traverse the Hashmap and print the character with its frequency of occurrence.

 Program to find the occurrence of a character in a string in Java

Here in this code, we take a Hashmap named as charCount which is of {character, Integer}. In this code what we will do is that if the hashmap contains the character we will increment the count by 1 and will put the character in the Hashmap else if the character is not present in the hashmap we will put the character to Hashmap with 1 as it’s value. finally, after traversing the string once we will print the Hashmap by using the command “entry.getKey()” and ” entry.getValue()”.

Hence, using Hashmap the solution becomes efficient as well as easy.

import java.io.*; import java.util.*;

class Occurence { 
// function for the character occurence frequency

static void characterOccurence (String inpstr) { 

//creating a Hashmap of {char,int}

 Hashmap<Character,Integer> charCount = new Hashmap<>(); 

// converting string to character

 char[] strArr = inpStr.toCharArray(); 

for (char ch : strArr) { 

if (charCount.containsKey(ch)) { 

// If char is present in Hashmap then

 // incrementing it's count by 1

 charCount.put(ch, charCount.get(ch) } 

else {

 // If char is not present in the Hashmap then 

// putting this char to Hashmap with 1 as it's value

 charCount.put(c, 1); } }

 // Printing the charCount

 for (Map.Entry entry : charCountMap.entrySet()) {

 System.out.println(entry.getKey() + " = " + entry.getValue()); }
}

//main function

public static void main(str [] args) {

String str = " Arjeet";

//calling function with str as argument

characterOccurence(str); }
}

Output:

A = 1

r = 1

j = 1

e = 2

t = 1

Hope the article is helpful to you.

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