Find number of occurrence of each of the unique characters in a string ?



Find number of occurrence of each of the unique characters in a string ?

  • In this program an approach using Hashmap in Java.
    • Declare a Hashmap in Java of {char, int}.
    • Traverse in the string, check if the Hashmap already contains the traversed character or not.
    • If it is present, then increase its count using get() and put() function in Hashmap.
    • Once the traversal is completed, traverse in the Hashmap and print the character and its frequency.

Example

Input: str = "Wikitechy"
Output: 
        W 1
        i 2
        k 1
        t 1
        e 1
        c 1
        h 1
        y 1

Sample Code in Java

// Java prorgam to count frequencies of 
// characters in string using Hashmap 
import java.io.*; 
import java.util.*; 
class OccurenceOfCharInString { 
	static void characterCount(String inputString) 
	{ 
		// Creating a HashMap containing char 
		// as a key and occurrences as a value 
		HashMap<Character, Integer> charCountMap = new HashMap<Character, Integer>(); 

		// Converting given string to char array 

		char[] strArray = inputString.toCharArray(); 

		// checking each char of strArray 
		for (char c : strArray) { 
			if (charCountMap.containsKey(c)) { 

				// If char is present in charCountMap, 
				// incrementing it's count by 1 
				charCountMap.put(c, charCountMap.get(c) + 1); 
			} 
			else { 

				// If char is not present in charCountMap, 
				// putting this char to charCountMap with 1 as it's value 
				charCountMap.put(c, 1); 
			} 
		} 

		// Printing the charCountMap 
		for (Map.Entry entry : charCountMap.entrySet()) { 
			System.out.println(entry.getKey() + " " + entry.getValue()); 
		} 
	} 

	// Driver Code 
	public static void main(String[] args) 
	{ 
		String str = "Wikitechy"; 
		characterCount(str); 
	} 
} 

Output

c 1
t 1
e 1
W 1
h 1
i 2
y 1
k 1


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