Given a string, the task is to write a program in Java which prints the number of occurrences of each character in a string.
Examples:
Input: str = "GeeksForGeeks" Output: r 1 s 2 e 4 F 1 G 2 k 2 o 1 Input: str = "Ajit" Output: A 1 t 1 i 1 j 1
An approach using frequency[] array has already been discussed in the previous post. In this program an approach using Hashmap in Java has been discussed.
- 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.
Below is the implementation of the above approach.
Java
// Java program to count frequencies of // characters in string using Hashmap import java.io.*;
import java.util.*;
class OccurrenceOfCharInString {
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 = "Ajit" ;
characterCount(str);
}
} |
Output:
A 1 t 1 i 1 j 1
Time complexity: O(n) where n is length of given string
Auxiliary Space: O(n)
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