Frequently Asked Java Program 26: Java Program to Find Occurrence of Each Char in a Given String Without Using Collection

Problem Statement:

Write a program to print occurrence of each character in given string without using Collection.

Example:-

Please enter the string to find occurrence of each char:
Make Selenium Easy
You entered: Make Selenium Easy
Occurrence of M : 2
Occurrence of A : 2
Occurrence of K : 1
Occurrence of E : 4
Occurrence of whitespace : 2
Occurrence of S : 2
Occurrence of L : 1
Occurrence of N : 1
Occurrence of I : 1
Occurrence of U : 1
Occurrence of Y : 1

Problem Solution:

This problem is easy to solve with the help of Collection framework of Java but in interview, you might be asked to solve without using Collection framework.

Logic:

1. We will pick first char from given string and iterate through each char of String to match if same char is present. We will use a counter with default value as zero for each iteration. Counter will be incremented by one if occurrence of char is found.
2. We will replace the char with empty char at end of each iteration causing reduction in length of actual string.  Iteration will be continued till the length of String is greater than one.
3. When (If) length of string is equal to 1, print occurrence of last char  as one.
4. We will give name to whitespace (” “) as “Whitespace” for better readability of output.

Java Programs:

package StringPrograms;

import java.util.Scanner;

public class occurrenceOfCharWithoutCollections {

	public static void occurrenceOfChar(String inputString) {

		// Converting input string to upper case
		inputString = inputString.toUpperCase();

		// We need to keep counting char till its length is greater than 1
		while (inputString.length() > 1) {

			// Resetting counter to zero for each iteration
			int counter = 0;
			// Extracting first char
			char c = inputString.charAt(0);
			// Iterating to find occurrence
			for (int j = 0; j < inputString.length(); j++) {
				// If matches, increment counter
				if (c == inputString.charAt(j)) {
					counter++;
				}
			}
			// Giving name to whitespace
			if (Character.isWhitespace(c)) {
				System.out.println("Occurrence of whitespace : " + counter);
			} else {
				System.out.println("Occurrence of " + inputString.charAt(0) + " : " + counter);
			}

			// Remove char whose occurrence is checked
			inputString = inputString.replace(Character.toString(inputString.charAt(0)), "");
		}
		// Printing single occurrence
		if (inputString.length() == 1) {
			System.out.println("Occurrence of " + inputString.charAt(0) + " : 1");
		}

	}

	public static void main(String[] args) {

		// User input for the string to know length
		Scanner sc = new Scanner(System.in);
		System.out.println("Please enter the string to find occurrence of each char:");

		String userInput = sc.nextLine();

		sc.close();

		System.out.println("You entered: " + userInput);

		occurrenceOfChar(userInput);
	}

}

Output:

[java]
Please enter the string to find occurrence of each char:
Make Selenium Easy
You entered: Make Selenium Easy
Occurrence of M : 2
Occurrence of A : 2
Occurrence of K : 1
Occurrence of E : 4
Occurrence of whitespace : 2
Occurrence of S : 2
Occurrence of L : 1
Occurrence of N : 1
Occurrence of I : 1
Occurrence of U : 1
Occurrence of Y : 1
==============================================================
Please enter the string to find occurrence of each char:
ABCDEF
You entered: ABCDEF
Occurrence of A : 1
Occurrence of B : 1
Occurrence of C : 1
Occurrence of D : 1
Occurrence of E : 1
Occurrence of F : 1
===============================================================
[/java]

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