jtulach@151: package api;
jtulach@151: 
jtulach@151: /** Class to simplify arithmetical operations, improved version to compute
jtulach@151:  * the sum for ranges, but only if one uses the new constructor to indicate
jtulach@151:  * need for new version.
jtulach@151:  *
jtulach@151:  * @author Jaroslav Tulach <jtulach@netbeans.org>
jtulach@151:  * @version 2.0
jtulach@151:  */
jtulach@151: // BEGIN: design.composition.arith2.0.enum
jtulach@151: public class Arithmetica {
jtulach@151:     private final Version version;
jtulach@151:     public enum Version { VERSION_1_0, VERSION_2_0 }
jtulach@151:     
jtulach@151:     public Arithmetica() {
jtulach@151:         this(Version.VERSION_1_0);
jtulach@151:     }
jtulach@151:     public Arithmetica(Version version) {
jtulach@151:         this.version = version;
jtulach@151:     }
jtulach@151: 
jtulach@151:     public int sumRange(int from, int to) {
jtulach@151:         switch (version) {
jtulach@151:             case VERSION_1_0:
jtulach@151:                 return sumRange1(from, to);
jtulach@151:             case VERSION_2_0:
jtulach@151:                 return sumRange2(from, to);
jtulach@151:             default:
jtulach@151:                 throw new IllegalStateException();
jtulach@151:         }
jtulach@151:     }
jtulach@152: // FINISH: design.composition.arith2.0.enum
jtulach@151:     
jtulach@151:     public int sumTwo(int one, int second) {
jtulach@151:         return one + second;
jtulach@151:     }
jtulach@151:     
jtulach@151:     public int sumAll(int... numbers) {
jtulach@187:         if (numbers.length == 0) {
jtulach@187:             return 0;
jtulach@187:         }
jtulach@151:         int sum = numbers[0];
jtulach@151:         for (int i = 1; i < numbers.length; i++) {
jtulach@151:             sum = sumTwo(sum, numbers[i]);
jtulach@151:         }
jtulach@151:         return sum;
jtulach@151:     }
jtulach@151:     
jtulach@151: 
jtulach@151:     private int sumRange1(int from, int to) {
jtulach@151:         int len = to - from;
jtulach@210:         if (len < 0) {
jtulach@210:             len = -len;
jtulach@210:             from = to;
jtulach@210:         }
jtulach@151:         int[] array = new int[len + 1];
jtulach@151:         for (int i = 0; i <= len; i++) {
jtulach@151:             array[i] = from + i;
jtulach@151:         }
jtulach@151:         return sumAll(array);
jtulach@151:     }
jtulach@151:     
jtulach@151:     private int sumRange2(int from, int to) {
jtulach@210:         return (from + to) * (Math.abs(to - from) + 1) / 2;
jtulach@151:     }
jtulach@151: }