CODEWITHSUNDEEP
javaarrays
Marcus
Marcus

Reputation: 115

Error trying to sum two different length arrays

I'm trying to make it so the elements of each array are added together to get a sum, regardless if one array is larger than the other. This is the error I'm getting

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5

The error is linked to line 13 or 23 depending on which array is bigger in my test class. ( pickedList[i] = listA[i] + listB[i]; are the error lines)

Edit: The code works if the arrays have the same number of elements, but when one is larger it crashes.

    public static int[] AddArray(int[] listA, int[] listB)

    { 
    int aLen = listA.length;
    int bLen = listB.length;
    int[] pickedList = null;
    //if array 1 is longer, make picklist have same number of elements then add
    //both array elements together
    if (aLen >= bLen)
    { pickedList = new int[aLen];
          for( int i = 0; i < aLen; i ++)
          {
            pickedList[i] =  listA[i] + listB[i]; 
          }
    }
     //if array 2 is longer, make picklist have same number of elements then add
    //both array elements together
    else 
    {
           pickedList = new int[bLen];
        for( int i = 0; i < bLen; i ++)
          {
            pickedList[i] =  listA[i] + listB[i] ;
          }   
    }
        return pickedList;
    }
}

Upvotes: 0

Views: 89

Answers (6)

Rustam
Rustam

Reputation: 6515

try this:

 public static int[] AddArray(int[] listA, int[] listB)

    { 
    int aLen = listA.length;
    int bLen = listB.length;
    int[] pickedList = null;
    int i,j;
    //if array 1 is longer, make picklist have same number of elements then add
    //both array elements together
    if (aLen >= bLen)
    {     pickedList = new int[aLen];
          for(  i = 0; i < bLen; i ++)
          {
            pickedList[i] =  listA[i] + listB[i]; 
          }
          for( j = i; j < aLen; j++) // listB exhaust so add remaining elements of listA  to pickedList
          {
            pickedList[j] =  listA[j] ; 
          }
    }
     //if array 2 is longer, make picklist have same number of elements then add
    //both array elements together
    else 
    {
        pickedList = new int[bLen];
        for(  i = 0; i < aLen; i ++)
          {
            pickedList[i] =  listA[i] + listB[i] ;
          }   
        for( j = i; j < bLen; j ++)// listA exhaust so add remaining elements of listB  to pickedList
        {
          pickedList[j] =  listB[j]; 
        }
    }
        return pickedList;
 }

Upvotes: 0

MH2K9
MH2K9

Reputation: 12039

If two arrays are 

arr1 = [1, 2, 3, 4, 5]
arr2 = [6, 7, 8]

The we can use lower length of two arrays as loop condition (ind < lower_length) to get rid from exception. eg,

int array1_length = arr1.length; // 5
int array2_length = arr1.length; // 3

Then we can get lower limit such ways

int limit = (array1_length > array2_length) ? array2_length : array1_length;

or

int limit = Math.max(array1_length, array2_length);

Then can use the limit in for loop, eg,

for(int ind = 0; ind < limit; ind++){
    //sum = arr1[ind] + arr2[ind];
}

I hope it will help you deeply.

Upvotes: 0

ewh
ewh

Reputation: 1024

public static int[] AddArray(int[] listA, int[] listB)
{
  int smallList[], bigList[], sums[];
  int pos;
  if (listA.length >= listB.length) {
    smallList = listB;
    bigList = listA;
  } else {
    smallList = listA;
    bigList = listB;
  }
  sums = new int[bigList.length];
  for (pos=0; pos < smallList.length; ++pos) {
    sums[pos] = smallList[pos] + bigList[pos];
  }
  for (; pos < bigList.length; ++pos) {
    sums[pos] = bigList[pos];
  }
  return sums;
}

Upvotes: 0

user1600704
user1600704

Reputation: 57

For your first if statement you have aLen >= bLen Then you loop for the length of aLen in a for loop. Inside this for loop, you try to access the elements of listB at index i. However, since listA is longer, the element listB[i] will not exist as the length of listA is longer than the length of listB.

Upvotes: 1

Elliott Frisch
Elliott Frisch

Reputation: 201429

I would use Math.max(int,int) to get the max length. Then declare the new array, then iterate the length adding the elements like

public static int[] addArray(int[] listA, int[] listB) {
    int aLen = listA.length;
    int bLen = listB.length;
    int len = Math.max(aLen, bLen);
    int[] pickedList = new int[len];
    for (int i = 0; i < len; i++) {
        if (i < aLen && i < bLen) {
            pickedList[i] = listA[i] + listB[i];
        } else if (i < aLen) {
            pickedList[i] = listA[i];
        } else {
            pickedList[i] = listB[i];
        }
    }
    return pickedList;
}

Upvotes: 1

Alex K
Alex K

Reputation: 8338

Your error is very simple:

if (aLen >= bLen)
    { pickedList = new int[aLen];
          for( int i = 0; i < aLen; i ++)
          {
            pickedList[i] =  listA[i] + listB[i];

you have that.

If alen is longer than blen, then if your forloop goes up to the length of a, you'll get an error because you have listB[i] - you're trying to access elements of B that just aren't there.

Let me make this clearer. Let's say array a has a length of 5, and array b has a length of 3. a is bigger than b, so you loop through i from 0 to 5. Everything will be fine fine for i = 0, i = 1, i = 2, but once you get to i = 3, there is no listB[i], because list B only has an elemnet in the 0, 1, and 2 position, so you get the error that you got.

I hope that helps. Good luck :)

Upvotes: 1

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