Closest.java

import java.util.Set;
import java.util.HashSet;
import java.util.Collection;
import java.util.Comparator;

public final class Closest {

   private Closest () {} // Don't instantiate this class!

   private static int index_i, index_j;

   // Need to return a PAIR!!!!
   public static void search (int[] data) {
      int diff = Integer.MAX_VALUE;
      for (int i=0; i<data.length; i++) {
         for (int j=i+1; j<data.length; j++) {
            final int d = Math.abs(data[i]-data[j]);
            if (d<diff) { index_i=i; index_j=j; diff=d; }
         }
      }
   }


   public static void main (final String [] args) {
      final int [] data  = new int [args.length];
      final int v = Integer.parseInt (args[0]);
      for (int i=0; i<args.length; i++) {
         final int k = Integer.parseInt (args[i]);
         data[i] = k;
      }

      search (data);

      System.out.printf ("data[%d]=%d, data[%d]=%d, diff=%d%n", index_i, data[index_i], index_j, data[index_j], Math.abs(data[index_i]-data[index_j]));
   }
}