package api;

 /** Class to simplify arithmetical operations, improved version to compute

  * the sum for ranges, but only if one uses the new constructor to indicate

  * need for new version.

  *

  * @author Jaroslav Tulach <jtulach@netbeans.org>

  * @version 2.0

  */

 // BEGIN: design.composition.arith2.0.enum

 public class Arithmetica {

     private final Version version;

     public enum Version { VERSION_1_0, VERSION_2_0 }

     public Arithmetica() {

         this(Version.VERSION_1_0);

     }

     public Arithmetica(Version version) {

         this.version = version;

     }

     public int sumRange(int from, int to) {

         switch (version) {

             case VERSION_1_0:

                 return sumRange1(from, to);

             case VERSION_2_0:

                 return sumRange2(from, to);

             default:

                 throw new IllegalStateException();

         }

     }

 // FINISH: design.composition.arith2.0.enum

     public int sumTwo(int one, int second) {

         return one + second;

     }

     public int sumAll(int... numbers) {

         if (numbers.length == 0) {

             return 0;

         }

         int sum = numbers[0];

         for (int i = 1; i < numbers.length; i++) {

             sum = sumTwo(sum, numbers[i]);

         }

         return sum;

     }

     private int sumRange1(int from, int to) {

         int len = to - from;

         int[] array = new int[len + 1];

         for (int i = 0; i <= len; i++) {

             array[i] = from + i;

         }

         return sumAll(array);

     }

     private int sumRange2(int from, int to) {

         return (from + to) * (to - from + 1) / 2;

     }

 }