palindrome-products: make class use instance methods

Fixes issue #377.

exercises/palindrome-products/src/example/java/Palindromes.java → exercises/palindrome-products/src/example/java/PalindromeCalculator.java

 import java.util.*;
 
-public class Palindromes {
+public class PalindromeCalculator {
 
-    public static SortedMap<Long, List<List<Integer>>> getPalindromeProductsWithFactors(int minFactor, int maxFactor) {
+    public SortedMap<Long, List<List<Integer>>> getPalindromeProductsWithFactors(int minFactor, int maxFactor) {
         SortedMap<Long, List<List<Integer>>> palindromeSortedList = new TreeMap<>();
         long num;
         List<List<Integer>> factors;
     }
 
     // http://stackoverflow.com/questions/23984654/how-to-print-all-palindromes-upto-1000-without-using-any-string-stringbuilder
-    private static long reverseNumber(long number) {
+    private long reverseNumber(long number) {
         if (number < 10l) {
             return number;
         }
         return result;
     }
 
-    private static boolean isPalindrome(long number) {
+    private boolean isPalindrome(long number) {
         return number == reverseNumber(number);
     }
 }

exercises/palindrome-products/src/test/java/PalindromesTest.java → exercises/palindrome-products/src/test/java/PalindromeCalculatorTest.java

+import org.junit.Before;
 import org.junit.Ignore;
 import org.junit.Test;
 
 
 import static junit.framework.TestCase.*;
 
-public class PalindromesTest {
+public class PalindromeCalculatorTest {
+    private PalindromeCalculator palindromeCalculator;
+
+    @Before
+    public void setup() {
+        palindromeCalculator = new PalindromeCalculator();
+    }
 
     @Test
     public void largestPalindromeFromSingleDigitFactors() {
         );
         final long expectedValue = 9l;
 
-        final SortedMap<Long, List<List<Integer>>> palindromes = Palindromes.getPalindromeProductsWithFactors(1, 9);
+        final SortedMap<Long, List<List<Integer>>> palindromes = palindromeCalculator.getPalindromeProductsWithFactors(1, 9);
 
         checkPalindromeWithFactorsMatchesExpected(expected, expectedValue, palindromes, palindromes.lastKey());
     }
         );
         final long expectedValue = 9009l;
 
-        final SortedMap<Long, List<List<Integer>>> palindromes = Palindromes.getPalindromeProductsWithFactors(10, 99);
+        final SortedMap<Long, List<List<Integer>>> palindromes = palindromeCalculator.getPalindromeProductsWithFactors(10, 99);
 
         checkPalindromeWithFactorsMatchesExpected(expected, expectedValue, palindromes, palindromes.lastKey());
     }
         );
         final long expectedValue = 121l;
 
-        final SortedMap<Long, List<List<Integer>>> palindromes = Palindromes.getPalindromeProductsWithFactors(10, 99);
+        final SortedMap<Long, List<List<Integer>>> palindromes = palindromeCalculator.getPalindromeProductsWithFactors(10, 99);
 
         checkPalindromeWithFactorsMatchesExpected(expected, expectedValue, palindromes, palindromes.firstKey());
     }
         );
         final long expectedValue = 906609l;
 
-        final SortedMap<Long, List<List<Integer>>> palindromes = Palindromes.getPalindromeProductsWithFactors(100, 999);
+        final SortedMap<Long, List<List<Integer>>> palindromes = palindromeCalculator.getPalindromeProductsWithFactors(100, 999);
 
         checkPalindromeWithFactorsMatchesExpected(expected, expectedValue, palindromes, palindromes.lastKey());
     }
         );
         final long expectedValue = 10201l;
 
-        final SortedMap<Long, List<List<Integer>>> palindromes = Palindromes.getPalindromeProductsWithFactors(100, 999);
+        final SortedMap<Long, List<List<Integer>>> palindromes = palindromeCalculator.getPalindromeProductsWithFactors(100, 999);
 
         checkPalindromeWithFactorsMatchesExpected(expected, expectedValue, palindromes, palindromes.firstKey());
     }