#23 Power of 2 test refactor and unit test.

Author: dmcreyno

src/jwave/tools/MathToolKit.java

@@ -181,17 +181,8 @@ public static int compose( int[ ] ancientEgyptianMultipliers ) throws JWaveExcep
    * @return true if is 2^p else false
    */
   public static boolean isBinary( int number ) {
-
-    boolean isBinary = false;
-
-    int power = (int)( Math.log( number ) / Math.log( 2. ) );
-
-    double result = 1. * Math.pow( 2., power );
-
-    if( result == number )
-      isBinary = true;
-
-    return isBinary;
+	// DLM#23 Power of 2 test
+    return number > 0 && ((number & (number - 1)) == 0);
 
   } // isBinary
 

test/jwave/tools/MathToolKitTest.java

@@ -0,0 +1,51 @@
+package jwave.tools;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class MathToolKitTest {
+	
+	private final int[] powersOfTwo= {1,2,4,8,16,32,64,128,256,512,1024,2048};
+	private final int[] notPowersOfTwo= {0,3,7,9,21,43,63,65,90,1001,};
+
+	/**
+	 * NOTE: Not certain what versions of Java we are supporting so I will avoid the iteration/collects enhancements.
+	 * 
+	 * Test for jwave.tools.MathToolKit.isBinary(int) : boolean, function. This test
+	 * attempts to verify that powers of two are correctly recognized.
+	 * 
+	 * The list of candidate numbers is infinite, making this test difficult to implement.
+	 * Feel free to add more numbers to the list but please do not add so many that the
+	 * test takes an unreasonable amount of time.
+	 */
+	@Test
+	public void testPowersOfTwo() {
+		MathToolKitTest.checkValue(powersOfTwo, true);
+	}
+
+	/**
+	 * NOTE: Not certain what versions of Java we are supporting so I will avoid the iteration/collects enhancements.
+	 * 
+	 * Test for jwave.tools.MathToolKit.isBinary(int) : boolean, function. This test
+	 * attempts to verify that powers of two are correctly recognized.
+	 * 
+	 * The list of candidate numbers is infinite, making this test difficult to implement.
+	 * Feel free to add more numbers to the list but please do not add so many that the
+	 * test takes an unreasonable amount of time.
+	 */
+	@Test
+	public void testNotPowersOfTwo() {
+		MathToolKitTest.checkValue(notPowersOfTwo, false);
+	}
+	
+	/**
+	 * 
+	 * @param values the list of integers to check
+	 * @param condition boolean indicating the expected result for ALL of the integers in the array.
+	 */
+	private static void checkValue(int[] values, boolean condition) {
+		for(int i = 0; i < values.length; i++) {
+			Assert.assertTrue("Value, " + values[i] +", failed test", condition == MathToolKit.isBinary(values[i]));
+		}
+	}
+}