A good answer might be:

Of course you remembered to initialize sum to zero, as below:

Complete Sum Method

Here is a complete program with the new method. All the previous methods of the class can be included where the comment indicates. 

class ArrayOps
{
  // . . . previous methods could go here 

  // add up all the elements in an array
  int sumElements ( int[] nums )
  {
    int sum = 0;

    for ( int j=0; j < nums.length; j++  )
      sum += nums[j];

    return  sum;
  }

}

class ArrayDemo
{
  public static void main ( String[] args ) 
  {
    ArrayOps operate = new ArrayOps();
    int[] ar1 =  { -20, 19, 1, 5, -1, 27, 19, 5 } ;
 
    System.out.println("The sum of elements is: " + 
      operate.sumElements( ar1 ) );   
  }

}

Notice how the main() method uses the method call as if it were a number: 

System.out.println("The sum of elements is: " + 
  operate.sumElements( ar1 ) );   
  --------------------------
             55

The method call returns the value 55 (the sum of all the array elements.) That value can be used just as if it had been written there as a constant.

QUESTION 14:

Would the following statement be correct as part of main()? 

int value =   operate.sumElements( ar1 ) / 4 + 32;