int cannot be converted to int []

Question

new to programming here and i keep getting the error message, 'incompatible types, int cannot be converted to int []', the question is to add R1& R2 together if they are of equal lengths and if not print a message that says 'the arrays must be same length', if that matters, not sure where im going wrong, any help would be greatly appreciated

 public int[] arrayAdd(int[] R1, int[] R2)
{
    int[] sumArray= new int[R1.length];

    if( R1.length!= R2.length)
    {
        System.out.println("The arrays must be same length");
}
else
{
    for(int i=0; i< R1.length; i++)
    for (int j=0; j<R2.length; j++)

    {

        sumArray= R1[i]+ R2[j]; // Error
    }
}
    return sumArray;
}

Answer 1

Your code is broken in many several ways, at least:

1. You declared returning an array but what is the value of it when inputs are of the wrong size? Manage such errors in better ways (stop, throw exception, return error code, etc). At least never display something at this place, this is not the place were you have to tackle the error, this is the place here you detect it, just report it to caller(s).
2. You (tried to) created space for the returned value but how could this be if conditions for having a return value is not met?
3. You used Java syntax to declare an array, int []sumArray should be `int sumArray[0].
4. You can't dynamically allocate an array like this, to capture a dynamic allocation you must use a pointer, an array is not a pointer. But a pointer can be set to the memory address of an allocated array, like int *sumArray = new int[10]
5. sumArray is an array so to set an element of it use sumArray[index] = ...

So this may be better:

public int *arrayAdd(int[] R1, int[] R2) {
    if( R1.length!= R2.length) {
        return nullptr;
    }
    int *sumArray= new int[R1.length];
    for(int i=0; i< R1.length; i++) {    
        sumArray[i] = R1[i]+ R2[i]; 
    }
    return sumArray;
}

---

After question editing

If you want to sum two arrays, element by element, then a single loop is sufficient...

Answer 2

           sumArray[i]= R1[i]+ R2[j]; // updated line

you need to assign to an array element, but you were doing it wrong.

Answer 3

Actually in that line sumArray is an integer array and you are assigning it as integer only and also you haven't declared variable j. Try this-

public int[] arrayAdd(int[] R1, int[] R2)
{
    int[] sumArray= new int[R1.length];

    if( R1.length!= R2.length)
    {
        System.out.println("The arrays must be same length");
    }
    else
    {
        for(int i=0; i< R1.length; i++)

        {

            sumArray[i]= R1[i]+ R2[i]; // Error
        }
    }
    return sumArray;
}

Answer 4

not sure where im going wrong

You are attempting to assign an int to a variable whose type is int[].

That is not legal ... and it doesn't make sense.

This:

   sumArray= R1[i]+ R2[j];

should be this

   sumArray[something_or_other] = R1[i] + R2[j];

... except that you have a bunch of other errors which mean that a simple "point fix" won't be correct.

Hint: you do not need nested loops to add the elements of two arrays.

-- Steve