Java BinarySearch

Can I get some help? I've tried many ways to make this work. I get array sorting and printing, but then my binary search function doesn't want to run and give me the correct results It always gives me - 1 Does it help?

public class BinarySearch {
public static final int NOT_FOUND = -1;
public static int binarySearch(double[] a,double key) {
    int low = 0;
    int high = a.length -1;
    int mid;
    while (low<=high) {
        mid = (low+high) /2;
        if (mid > key) 
            high = mid -1;
        else if (mid < key) 
            low = mid +1;
        else 
            return mid;
    }
    return NOT_FOUND;
}
public static void main(String[] args) {
    double key = 10.5,index;
    double a[] ={10,5,4,10.5,30.5};
    int i;
    int l = a.length;
    int j;
    System.out.println("The array currently looks like");
    for (i=0; i<a.length; i++)
        System.out.println(a[i]);
    System.out.println("The array after sorting looks like");
    for (j=1; j < l; j++) {
        for (i=0; i < l-j; i++) {
            if (a[i] > a[i+1]) {
                double temp = a[i];
                a[i] = a[i+1];
                a[i+1] = temp;
            }
        }
    }
    for (i=0;i < l;i++) {
        System.out.println(a[i]);
    }
    System.out.println("Found " + key + " at " + binarySearch(double a[],key));
}   
}

Solution

You don't actually compare with array values stay

while (low <= high) {
      mid = (low + high) / 2;
      if (mid > key) {
          high = mid - 1;
      } else if (mid < key) {
          low = mid + 1;
      } else {
          return mid;
      }
}

Instead, use this section

while (low <= high) {
        mid = (low + high) / 2;
        if (a[mid] > key) {
            high = mid - 1;
        } else if (a[mid] < key) {
            low = mid + 1;
        } else {
            return mid;
        }
    }

You find the correct index, but what you do is you just compare the index number with your key, which is obviously incorrect When you write [mid], you actually compare your key with the number in the middle of the index

The last line of code is also a compilation error. It should be

System.out.println("Found " + key + " at " + binarySearch(a,key));