[FIXED] Trying to count occurence of each letter in String in Java

Issue

I am not able to get the correct occurrence of each letter present in the string. What is wrong with my code?

Code:

public class consecutiveCharacters {
    public static String solve(String A, int B) {
        HashMap<String, Integer> map = new HashMap<>();
        for (int i=0;i<A.length();i++) {
            Integer value = map.get(A.charAt(i));
            if(value == null){
                map.put(String.valueOf(A.charAt(i)),1);
            }
            else {
                map.put(String.valueOf(A.charAt(i)),i+1);
            }
        }
        System.out.println(map); 
        String text = "i feel good";
        return text;
    }

    public static void main(String[] args) {
        solve("aabbccd",2);
    }
}

The output of the map should be:

{a=2, b=2, c=2, d=1}

Yet the output that the above code is giving is:

{a=1, b=1, c=1, d=1}

Solution

Using Map.merge() you can rid of checking this yourself:

Map<Character, Integer> map = new HashMap<>();
for( char c : A.toCharArray()) {
    map.merge(c, 1, Integer::sum);                      
}

merge() takes 3 parameters:

• A key which is the character in your case
• A value to put for the key, which is 1 in your case
• A merge bi-function to combine the new and existing values if the entry already existed. Integer::sum refers to Integer's method static int sum(int a, int b) which basically is the same as your value + 1.

Answered By - Thomas