ArrayIndexOutOfBounds Exception for some input values

Question

The following is a part of my code. For some values of bands and bandRows the code seems to run perfectly alright. But for some it gives an ArrayIndexOutOfBounds exception. Any ideas where I might have gone wrong? I cannot find any mistake in the code. Thanks in advance

for(int i=0; i<bands; i++)
        {
            int a=0;
            while(a<bucketSize) 
            { 
                bandBuckets[i][a] = new ArrayList();
                a++;
            }
        }  

    for (int i = 0; i < bands; i++) 
            {          
                for (int j = 0; j < preprocessedList.size(); j++) 
                {
                    int[][] forBuckets = new int[bands][bandRows];

                    for (int k = 0; k < bandRows; k++) 
                    {
                        Arrays.fill(forBuckets[i], Bands[i][k][j]);

                    }

                    bandBuckets[i][h.hashBands(forBuckets[i], bucketSize)].add(j);

                }
            }

Here's the h.hashBands() function which is in another class

 public int hashBands(int[] in, int bucketSize) 
        {

            int hashVal = 0;
            int k = in.length;
            int base = 3;
            for (int i = 0; i < in.length; i++) {
               // for (int j = 0; i < in[i].length; i++) 
                    hashVal += in[i] * Math.pow(base, k - i - 1);
            }
            return hashVal % bucketSize;

        }

Too many arrays, too many dimensions... What is Bands[i][k][j] .... are those dimensions right .... — rolfl
– rolfl, Commented Nov 20, 2013 at 4:11
yeah they are right. It works perfectly well for some inputs. Only for some, it gives the error — zim
– zim, Commented Nov 20, 2013 at 4:13

gabrielwong · Accepted Answer · 2013-11-20 04:16:16Z

1

Perhaps there is an overflow in your hashBands() function.

The max value for an int is 2³¹ - 1. hashVal will overflow when k - i - 1 is greater than 19. In Java, exceptions aren't thrown for overflows and underflows. Consider using a BigInteger and its modPow() function.

answered Nov 20, 2013 at 4:16

gabrielwong

3011 silver badge6 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

sumitsabhnani · Accepted Answer · 2013-11-20 04:12:16Z

0

Can you tell where exactly you are getting ArrayIndexOutOfBoundException. Seeing your code it seems that there might be some problem while returning from hashBands() function. It might be returning something greater than expected.

bandBuckets[i][h.hashBands(forBuckets[i], bucketSize)]

For the 2nd dimension of this array h.hashBands(forBuckets[i], bucketSize) --> this value might be greater than the expected value for that part.....

answered Nov 20, 2013 at 4:12

sumitsabhnani

3101 silver badge6 bronze badges

1 Comment

zim Over a year ago

Yes it's that line bandBuckets[i][h.hashBands(forBuckets[i], bucketSize)].add(j); But that value should be less than bucketSize. The function hashBands() return the mod of hash value by bucketSize (hashVal % bucketSize). So obviously it is less than the bucketSize..

Collectives™ on Stack Overflow

ArrayIndexOutOfBounds Exception for some input values

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related