Java Program to Find Frequency of each Character in a String

Write a Java Program to Find Frequency of each Character in a String with an example. First, we declared the 256 size charFreq integer array. Next, we traversed the freqStr string and assigned character frequency to charFreq array. Then, we used another for loop to return the character frequency.

import java.util.Scanner;

public class FreqOfEachChar {
	private static Scanner sc;
	public static void main(String[] args) {
		String freqStr;
		int i = 0, j = 0;
		int[] charFreq = new int[256];
		
		sc= new Scanner(System.in);

		System.out.print("\nPlease Enter String to find Frequency of each Char =  ");
		freqStr = sc.nextLine();
		
		while(i < freqStr.length())
		{
			charFreq[freqStr.charAt(i)]++;
			i++;
		}
		while(j < 256) {
			if(charFreq[j] != 0) {
				System.out.format("\n'%c' Character Occurs %d Times ", j, charFreq[j]);	
			}
			j++;
		}
	}
}

Java Program to Find Frequency of each Character in a String using For Loop

import java.util.Scanner;

public class FreqOfEachChar2 {
	private static Scanner sc;
	public static void main(String[] args) {
		String freqStr;
		int i;
		int[] charFreq = new int[256];
		
		sc= new Scanner(System.in);

		System.out.print("\nPlease Enter String to find Frequency of each Char =  ");
		freqStr = sc.nextLine();
		
		for(i = 0; i < freqStr.length(); i++)
		{
			charFreq[freqStr.charAt(i)]++;
		}
		for(i = 0; i < 256; i++) {
			if(charFreq[i] != 0) {
				System.out.format("\n'%c' Character Occurs %d Times ", i, charFreq[i]);	
			}
		}
	}
}

Java frequency of each string character output

Please Enter String to find Frequency of each Char =  java program

' ' Character Occurs 1 Times 
'a' Character Occurs 3 Times 
'g' Character Occurs 1 Times 
'j' Character Occurs 1 Times 
'm' Character Occurs 1 Times 
'o' Character Occurs 1 Times 
'p' Character Occurs 1 Times 
'r' Character Occurs 2 Times 
'v' Character Occurs 1 Times 

It is another way to write a Java Program to return each character frequency in a String.

import java.util.Scanner;

public class FreqOfEachChar3 {
	private static Scanner sc;
	public static void main(String[] args) {
		String freqStr;
		int i;
		int[] charFreq = new int[256];
		
		sc= new Scanner(System.in);

		System.out.print("\nEnter String to find Frequency of each Char =  ");
		freqStr = sc.nextLine();
		
		for(i = 0; i < freqStr.length(); i++)
		{
			char ch = freqStr.charAt(i);
			if(ch >= 'a' && ch <= 'z') {
				charFreq[ch - 'a']++;
			}
			else if(ch >= 'A' && ch <= 'Z') {
				charFreq[ch - 'A']++;
			}
		}
		for(i = 0; i < 256; i++) {
			if(charFreq[i] != 0) {
				System.out.format("\n'%c' Character Occurs %d Times ", i + 'a', charFreq[i]);	
			}
		}
	}
}

Enter String to find Frequency of each Char =  hello world

'd' Character Occurs 1 Times 
'e' Character Occurs 1 Times 
'h' Character Occurs 1 Times 
'l' Character Occurs 3 Times 
'o' Character Occurs 2 Times 
'r' Character Occurs 1 Times 
'w' Character Occurs 1 Times 

This Java code to find string character frequency is the same as the above. Here, we separated the character frequency logic using Java functions.

import java.util.Scanner;

public class FreqOfEachChar4 {
	private static Scanner sc;
	public static void main(String[] args) {
		String freqStr;
	
		sc= new Scanner(System.in);

		System.out.print("\nEnter String to find Frequency of each Char =  ");
		freqStr = sc.nextLine();
		
		FreqOfEachChar(freqStr);		
	}
	
	public static void FreqOfEachChar(String freqStr) {
		int i;
		int[] charFreq = new int[256];
		
		for(i = 0; i < freqStr.length(); i++)
		{
			charFreq[freqStr.charAt(i)]++;
		}
		for(i = 0; i < 256; i++) {
			if(charFreq[i] != 0) {
				System.out.format("\n'%c' Character Occurs %d Times ", i, charFreq[i]);	
			}
		}
	}
}

Enter String to find Frequency of each Char =  tutorial gateway

' ' Character Occurs 1 Times 
'a' Character Occurs 3 Times 
'e' Character Occurs 1 Times 
'g' Character Occurs 1 Times 
'i' Character Occurs 1 Times 
'l' Character Occurs 1 Times 
'o' Character Occurs 1 Times 
'r' Character Occurs 1 Times 
't' Character Occurs 3 Times 
'u' Character Occurs 1 Times 
'w' Character Occurs 1 Times 
'y' Character Occurs 1 Times