Java递归二进制搜索抛出界外异常？

Question

Hey, I have been asked to write a recursive binary search for my data structure class in university, but i'm having a slight problem. When i search for a number that is out of bounds (over 10 in this case) it throws an out of bounds exception. I understand why it's doing it, due to the array not having >10 spaces, but i don't know how to work around it. Any ideas?

The array that im searching is an ordered array 1 - 10 (index 0 - 9).

 public int recursiveBinarySearch(int[] anArray, int searchedNumber, int min, int max) {

    if (min > max)
        {
                System.out.println(searchedNumber + " is not present in tha array.");
                //return -1 to show that the value has not been found
        return -1;
        }
        // find the centre of the array
        int centre = (min + max) / 2;

    if (anArray[centre] == searchedNumber)
        {
                System.out.println(searchedNumber + " was found at index " + centre);
        return centre;
        }

        if (anArray[centre] < searchedNumber)
        {
        return recursiveBinarySearch(anArray, searchedNumber, centre+1, max);
        }

        return recursiveBinarySearch(anArray, searchedNumber, min, centre-1);

 }

Answer 1

public int recursiveBinarySearch(...) {
    if (max >= array.length) {
        max = array.length - 1;
    }
    if (min < 0) {
        min = 0;
    }
    ... rest of the code
} 

PS Not to be a nagger, but I would also recommend using consistent indentation. Believe me, it helps greatly in writing bug-free programs.

Answer 2

I suppose it starts with min = 0 and max = 9 , then it goes

min = 0, max = 9, c = (0+9 / 2) = 4
min = 5, max = 9, c = (6+9 / 2) = 7
min = 8, max = 9, c = (8+9 / 2) = 8
min = 9, max = 9, c = (9+9 / 2) = 9
min = 10, max = 9, ...

As you can see it gets over the bound, min = 10 will of course cause problems. To avoid that just widen the initial condition:

if (min > max || min > Array.length -1 || max < 0)
  // not found!

so that if your going over the array in any of two directions then the requested element won't be found.