Question

How to sum all the duplicate numbers in array with Java

Answer 1

import java.util.Arrays;
  
public class Program {
    public static void main(String[] args) {
        Integer[] arr = {2, 3, 4, 2, 1, 1, 7, 5, 8, 9, 5, 3};
          
        // 2 + 2 + 3 + 3 + 1 + 1 + 5 + 5 = 22
          
        System.out.println(sumUniqueNumbers(arr));
    }
  
    public static int sumUniqueNumbers(Integer[] arr) {
        int result = 0;
        for (int i = 0; i < arr.length; i++) {
            // if (first index 1 != last index 1) -> duplicates
            if (Arrays.asList(arr).indexOf(arr[i]) != Arrays.asList(arr).lastIndexOf(arr[i])) {
                result += arr[i];
            }
        }
        return result;
    }
}
  
  
   
/*
run
   
22
   
*/

 

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