Question

Getting errors with my Java Program. I have to do a simple program that uses binary search to pick a value out of an array. Here's what I have-

Answer 1

public class Bsearch
{
public static final int NOT_FOUND= -1;
public static int binarySearch( int [] a, int x)
{
int low= 0;
int high = a. length - 1;
int mid;
while( low <= high)
{
mid = ( low + high ) / 2;
if( a[ mid ].compareTo( x ) < 0 )
low = mid + 1;
else if( a[ mid ].compareTo( x ) > 0 )
high = mid - 1;
else
return mid;
}
return NOT_FOUND;
}
public static void main(String[] args)
{
int SIZE = 6;
int [] a = new Integer [ SIZE ]={ 10,-3,5,24,45.3,10.5 };
System.out.println("45.3 Found" +binarySearch(a, 45.3));
}
}

Answer 2

All my errors are coming from this section int SIZE = 6;
int [] a = new Integer [ SIZE ]={ 10,-3,5,24,45.3,10.5 };
System.out.println("45.3 Found" +binarySearch(a, 45.3));

Answer 3

it would help if you gave us the stack trace

Answer 4

Hi. Its because you use int and Integer simultaneoulsy for the declaration. It is not same. "int" is a primitve data type. "Integer" is an object.
http://mindprod.com/jgloss/intvsinteger.html
refer this link for the difference.
Also, you cannot use two assignment operations combined.
try using this line instead :
int[] a = {10,-3,5,24,45.3,10.5};
It automatically assumes that the size is 6.
If you want the size to be as you desire, you can use this:
int[] a=new int[SIZE];
a= {10,-3,5,24,45.3,10.5};
In this case the size of the array will be the value of "SIZE".
Smalll Tip : Make sure the value of "SIZE" is more than the number you are storing in it.

Answer 5

Also, I noticed that the binarySearch() you have defined, will only work for already sorted array. So, kindly sort the array before you pass the array to the function.
Tip : There are lots of sorting functions you can read about. Bubble sort, Selection sort are quite easy to understand.

Answer 6

```
int [] a = new Integer [ SIZE ]={ 10,-3,5,24,45.3,10.5 };
```
45.3 is not an int, it's a float or double; that will contribute towards an error in your program.

Answer 7

'Narrowing conversions' are not automatic in java; just Widening Conversions; this is to prevent data loss.. A narrowing conversion is the move to a smaller data-type(in terms of memory), and a widening conversion is the move to a bigger data-type. so if you manually did a narrowing conversion on 45.3 to an int, you would need to use a cast operator.

```
int a = (int)45.3;
```
but alas, ints do not store decimals, so the value stored in 'a' is now 45.