Find duplicate characters in a String and count the number of occurances using Java

Question

How can I find the number of occurrences of a character in a string?

For example: The quick brown fox jumped over the lazy dog.

Some example

Answer 1

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String reverse1;
        String reverse2;
        int count = 0;
        while(n > 0)
        {
            String A = sc.next();
            String B = sc.next();
            reverse1 = new StringBuffer(A).reverse().toString();
            reverse2 = new StringBuffer(B).reverse().toString();
            if(!A.equals(reverse1))
            {
                for(int i = 0; i < A.length(); i++)
                {
                    for(int j = 0; j < A.length(); j++)
                    {
                        if(A.charAt(j) == A.charAt(i))
                        {
                            count++;
                        }
                    }
                    if(count % 2 != 0)
                    {
                        A.replace(A.charAt(i),"");
                        count = 0;
                    }
                }
                System.out.println(A);
            }
            n--;
        } 
    }
}