fixed problems of code review from @havanagrawal

DDullahan · DDullahan · commit c85caf50d670 · 2019-05-03T08:56:07.000+08:00
https://github.com/TheAlgorithms/Java/pull/731/files/7216f28cb318b32eedf420d2fb6274254dd671ff
diff --git a/src/main/java/com/Others/FastPower.java b/src/main/java/com/Others/FastPower.java
@@ -13,11 +13,11 @@ public class FastPower {
     public static BigInteger calculate(BigInteger n, BigInteger k, BigInteger mod) {
         BigInteger ans = BigInteger.ONE;
         while (!k.equals(BigInteger.ZERO)) {
-            int odd = k.mod(new BigInteger("2")).compareTo(BigInteger.ZERO);
-            if(odd == 1){
+            int odd = k.mod(BigInteger.valueOf(2)).compareTo(BigInteger.ZERO);
+            if(odd > 0){
                 ans = ans.multiply(n).mod(mod);
             }
-            k = k.divide(new BigInteger("2"));
+            k = k.divide(BigInteger.valueOf(2));
             n = n.multiply(n).mod(mod);
         }
         return ans.mod(mod);
diff --git a/src/main/java/com/Others/FastPowerTest.java b/src/main/java/com/Others/FastPowerTest.java
@@ -8,33 +8,25 @@
 
 public class FastPowerTest {
 
-    @Test
-    public void test() {
-        System.out.println("Long Type:");
-        long result;
-        result = FastPower.calculate(2, 2, 10);
-        assertEquals(result, 4);
-        System.out.println("The result of power(2,2) mod 10 is " + result);
-
-        result = FastPower.calculate(100, 1000, 20);
-        assertEquals(result, 0);
-        System.out.println("The result of power(100, 1000) mod 20 is " + result);
-
-        result = FastPower.calculate(123456, 123456789, 234);
-        System.out.println("The result of power(123456, 123456789) mod 234 is " + result);
-
+    void testLong(long n, long k, long m){
+        long result = FastPower.calculate(n,k,m);
+        assertEquals(result, BigInteger.valueOf(n).modPow(BigInteger.valueOf(k), BigInteger.valueOf(m)).longValue());
+    }
 
-        System.out.println("BigInteger Type:");
-        BigInteger bigResult;
-        bigResult = FastPower.calculate(BigInteger.TEN, BigInteger.TEN, new BigInteger("4"));
-        assertEquals(bigResult, BigInteger.ZERO);
-        System.out.println("The bigResult of power(10, 10) mod 4 is " + bigResult);
+    void testBigInteger(BigInteger n, BigInteger k, BigInteger m){
+        BigInteger result = FastPower.calculate(n,k,m);
+        assertEquals(result, n.modPow(k,m));
+    }
 
-        bigResult = FastPower.calculate(new BigInteger("123456"), new BigInteger("123456789"), new BigInteger("234"));
-        System.out.println("The bigResult of power(123456, 123456789) mod 234 is " + bigResult);
+    @Test
+    public void test() {
+        testLong(2,2,10);
+        testLong(100,1000,20);
+        testLong(123456,123456789,234);
 
-        bigResult = FastPower.calculate(new BigInteger("123456789101112"), new BigInteger("12345678910111213"), new BigInteger("567890"));
-        System.out.println("The bigResult of power(123456789101112, 12345678910111213) mod 567890 is " + bigResult);
+        testBigInteger(BigInteger.TEN,BigInteger.TEN, BigInteger.valueOf(4));
+        testBigInteger(new BigInteger("123456"), new BigInteger("123456789"), new BigInteger("234"));
+        testBigInteger(new BigInteger("123456789101112"), new BigInteger("12345678910111213"), new BigInteger("567890"));
 
     }
 }
