"java.lang.ArrayIndexOutOfBoundsException: 1" when the size of the array > the index

Question

public static int[] allBetween()
    {
        Scanner input = new Scanner(System.in);
        int first;
        int last;

        System.out.println("Enter the first number");
        first = input.nextInt();
        System.out.println("Enter the last number");
        last = input.nextInt();

        int[] between = {((last - first) + 1)};

        for(int count = 0; count <= (last - first); count++)
        {
            between[count] = (first + count);
        }

        return between;
    }

I'm a little rusty and I dont't see the issue here, I have tried manually assigning the size of the array to 100 and first and last to 1 and 5 but it still returns the same error.

any ideas?

this is my first post on stack over flow, Please correct me if I'm posting in an incorrect manner

There's nothing wrong with your post, but before you post about runtime errors you should probably debug more. — keyser
– keyser, Commented Aug 15, 2013 at 15:23

Rohit Jain · Accepted Answer · 2013-08-15 15:12:56Z

4

The below statement:

int[] between = {((last - first) + 1)};

initializes the array with just a single element, with the value - last - first + 1

Change it to:

int size = last - first + 1;
int[] between = new int[size];

And then, you can change your loop to:

for(int count = 0; count < size; ++count)

answered Aug 15, 2013 at 15:12

Rohit Jain

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Comments

kosa · Accepted Answer · 2013-08-15 15:12:37Z

3

Issue is:

int[] between = {((last - first) + 1)}; //initializes array with value

You have only one value in this array at index 0, and if last-first is greater than ZERO, you will end up having ArrayIndexOutOfBoundsException.

Read arrays tutorial for more information.

answered Aug 15, 2013 at 15:12

kosa

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Comments

nanofarad · Accepted Answer · 2013-08-15 15:13:09Z

3

This line:

int[] between = {((last - first) + 1)};

creates an array with a single element whose value is equal to ((last - first) + 1.

Use:

int[] between = new int[(last-first)+1];

anyway, to iterate through it, you can use a nicer more readable/idiomatic construct:

for(int count = 0; count < between[length]; count++)
{
    between[count] = (first + count);
}

Remember that arrays are addressed and dimensioned by brackets, created explicitly with braces.

Also, between[count] = (first + count); looks suspicious. Make sure that's really what you want it to do, namely to set the count^th element of between to first+count. That would just make an array filled with first, first+1, ....

answered Aug 15, 2013 at 15:13

nanofarad

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Comments

jlordo · Accepted Answer · 2013-08-15 15:18:20Z

3

you should replace

int[] between = {((last - first) + 1)};

with

int[] between = new int[((last - first) + 1)];

because your version always creates an array of length 1. See this for example:

int[] foo = {22};

is an int[] of length 1 and foo[0] is 22. Whereas

int[] bar = new int[33];

createas an array of length 33 where each index stores the default value 0.

edited Aug 15, 2013 at 15:18

answered Aug 15, 2013 at 15:12

jlordo

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