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

In this tutorial, we will write a Java program to find the occurrence of a character in a String.

Program to find occurrence of a character in a string

In this program we are finding the occurrence of each character in a String. To do this we are first creating an array of size 256 (ASCII upper range), the idea here is to store the occurrence count against the ASCII value of that character. For example, the occurrence of ‘A’ would be stored in counter[65] because ASCII value of A is 65, similarly occurrences of other chars are stored in against their ASCII index values.

We are then creating an another array array to hold the characters of the given String, then we are comparing them with the characters in the String and when a match is found the count of that particular char is displayed using counter array.

class JavaExample {  

   static void countEachChar(String str) 
   { 
	//ASCII values ranges upto 256
	int counter[] = new int[256]; 

	//String length
	int len = str.length(); 

	/* This array holds the occurrence of each char, For example
	 * ASCII value of A is 65 so if A is found twice then 
	 * counter[65] would have the value 2, here 65 is the ASCII value
	 * of A
	 */
	for (int i = 0; i < len; i++) 
		counter[str.charAt(i)]++; 

	// We are creating another array with the size of String
	char array[] = new char[str.length()]; 
        for (int i = 0; i < len; i++) { 
	   array[i] = str.charAt(i); 
	   int flag = 0; 
	   for (int j = 0; j <= i; j++) { 

		/* If a char is found in String then set the flag 
		 * so that we can print the occurrence
		 */
		if (str.charAt(i) == array[j])  
			flag++;                 
	   } 

	   if (flag == 1)  
	      System.out.println("Occurrence of char " + str.charAt(i)
		 + " in the String is:" + counter[str.charAt(i)]);             
	} 
   } 
   public static void main(String[] args) 
   {  
	String str = "beginnersbook"; 
	countEachChar(str); 
   } 
}

Output:

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