Make hamming use instance methods

Fixes issue #346

exercises/hamming/src/example/java/Hamming.java

@@ -1,6 +1,15 @@
 public class Hamming {
+    private final int hammingDistance;
 
-    public static int compute(String leftStrand, String rightStrand) {
+    public Hamming(String leftStrand, String rightStrand) {
+        hammingDistance = computeHammingDistance(leftStrand, rightStrand);
+    }
+
+    public int getHammingDistance() {
+        return hammingDistance;
+    }
+
+    private int computeHammingDistance(String leftStrand, String rightStrand) {
         if(leftStrand.length() != rightStrand.length()) {
             throw new IllegalArgumentException("leftStrand and rightStrand must be of equal length.");
         }
@@ -13,7 +22,7 @@ public class Hamming {
         return distance;
     }
 
-    private static int hammingContributionAt(int index, String leftStrand, String rightStrand) {
+    private int hammingContributionAt(int index, String leftStrand, String rightStrand) {
       return leftStrand.charAt(index) != rightStrand.charAt(index) ? 1 : 0;
     }
 

exercises/hamming/src/test/java/HammingTest.java

@@ -7,64 +7,63 @@ import org.junit.Rule;
 import org.junit.rules.ExpectedException;
 
 public class HammingTest {
-    
 
     @Rule
     public ExpectedException thrown = ExpectedException.none();
     
     @Test
     public void testNoDifferenceBetweenIdenticalStrands() {
-        assertThat(Hamming.compute("A", "A"), is(0));
+        assertThat(new Hamming("A", "A").getHammingDistance(), is(0));
     }
 
     @Ignore
     @Test
     public void testHammingDistanceForSingleNucleotideStrand() {
-        assertThat(Hamming.compute("A", "G"), is(1));
+        assertThat(new Hamming("A", "G").getHammingDistance(), is(1));
     }
 
     @Ignore
     @Test
     public void testHammingDistanceForSmallStrand() {
-        assertThat(Hamming.compute("AG", "CT"), is(2)); 
+        assertThat(new Hamming("AG", "CT").getHammingDistance(), is(2));
     }
 
     @Ignore
     @Test
     public void testSmallHammingDistance() {
-        assertThat(Hamming.compute("AT", "CT"), is(1));
+        assertThat(new Hamming("AT", "CT").getHammingDistance(), is(1));
     }
 
     @Ignore
     @Test
     public void testSmallHammingDistanceInLongerStrand() {
-        assertThat(Hamming.compute("GGACG", "GGTCG"), is(1));
+        assertThat(new Hamming("GGACG", "GGTCG").getHammingDistance(), is(1));
     }
 
     @Ignore
     @Test
     public void testValidatesFirstStrandNotLonger() {
         thrown.expect(IllegalArgumentException.class);
-        Hamming.compute("AAAG", "AAA");                
+        new Hamming("AAAG", "AAA");
     }
 
     @Ignore
     @Test
     public void testValidatesOtherStrandNotLonger() {
         thrown.expect(IllegalArgumentException.class);
-        Hamming.compute("AAA", "AAAG");
+        new Hamming("AAA", "AAAG");
     }
 
     @Ignore
     @Test
     public void testLargeHammingDistance() {
-        assertThat(Hamming.compute("GATACA", "GCATAA"), is(4));
+        assertThat(new Hamming("GATACA", "GCATAA").getHammingDistance(), is(4));
     }
 
     @Ignore
     @Test
     public void testHammingDistanceInVeryLongStrand() {
-        assertThat(Hamming.compute("GGACGGATTCTG", "AGGACGGATTCT"), is(9));
+        assertThat(new Hamming("GGACGGATTCTG", "AGGACGGATTCT").getHammingDistance(), is(9));
     }
 
 }