Binary.java

public final class Binary {

   public static int search (final int v, final int[] data) {
      return search (v, data, 0, data.length);
   }

   public static int search (final int v, final int[] data, final int last) {
      return search (v, data, 0, last);
   }

   // Search everything from 'first' to 'last-1' (inclusive)
   public static int search (final int v, final int[] data, final int first, final int last) {
      assert 0<=first && first<=data.length;
      assert 0<=last && last<=data.length;
      int low = first, high = last-1;
      while (low <= high) {
         final int mid = (low+high)>>>1;  // works even when + overflows
         assert low<=mid;
         assert mid<=high;
         if (data[mid] == v) {
            return mid;    // EXIT; v found
         } else if (data[mid] < v) {
            System.out.printf ("data[%d]=%d is too low%n", mid, data[mid]);
            // Everything from 'low' to 'mid' is excluded.
            assert low < mid+1;
            low = mid+1;
         } else {
            assert data[mid] > v;
            System.out.printf ("data[%d]=%d is too high%n", mid, data[mid]);
            // Everything from 'mid' to 'high' is excluded.
            assert mid-1 < high;
            high = mid-1;
         }
      }
      return -1;  // v not found
   }

   public static void main (final String [] args) {
      final int [] data  = new int [args.length-1];
      final int v = Integer.parseInt (args[0]);
      int n = 0;
      for (int i=1; i<args.length; i++) {
         try {
            data[n++] = Integer.parseInt (args[i]);
         } catch (NumberFormatException ex) {
            ex.printStackTrace (System.err);
         }
      }
      System.out.printf ("Searching for %d in %s%n",
            n, java.util.Arrays.toString(data));
      final int i = search (v, data, n);
      if (i==-1) {
         System.out.printf ("%d not found%n", v);
      } else {
         System.out.printf ("%d found at index %d%n", v, i);
      }
   }
}