Problem_3.java

package strings;

import java.util.Scanner;

//* Problem Title ==> Find Duplicate characters in a string
public class Problem_3 {

    static final int NO_OF_CHARS = 256;

    // Fills count array with frequency of characters
    static void fillCharCounts(String str, int[] count) {
        for (int i = 0; i < str.length(); i++)
            count[str.charAt(i)]++;
    }

    static void printDups(String str) {
        // Create an array of size 256 and fill count of every character in it
        int[] count = new int[NO_OF_CHARS];
        fillCharCounts(str, count);

        for (int i = 0; i < NO_OF_CHARS; i++)
            if (count[i] > 1)
                System.out.println((char) (i) + ", count = " + count[i]);
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        printDups(str);
        sc.close();
    }
}