BAEL-1076 How to get a number of digits in an int? (#2457)

* BAEL-1076 How to get a number of digits in an int? Six different ways to find the number of digits in an integer. * BAEL-1076 How to get a number of digits in an int? * Update NumberOfDigits.java
2017-08-26 00:54:43 +05:30
parent d492c6f4d8
commit 09d10ac85f
4 changed files with 355 additions and 0 deletions
--- a/core-java/src/test/java/com/baeldung/numberofdigits/NumberOfDigitsIntegrationTest.java
+++ b/core-java/src/test/java/com/baeldung/numberofdigits/NumberOfDigitsIntegrationTest.java
@@ -0,0 +1,100 @@
+package com.baeldung.numberofdigits;
+
+import org.junit.Assert;
+import org.junit.Assume;
+import org.junit.experimental.theories.DataPoints;
+import org.junit.experimental.theories.Theories;
+import org.junit.experimental.theories.Theory;
+import org.junit.runner.RunWith;
+
+@RunWith(Theories.class)
+public class NumberOfDigitsIntegrationTest {
+
+    @DataPoints
+    public static int[][] lowestIntegers()
+    {
+      return new int[][]{
+          {1, 1}, 
+          {2, 10}, 
+          {3, 100}, 
+          {4, 1000}, 
+          {5, 10000}, 
+          {6, 100000}, 
+          {7, 1000000}, 
+          {8, 10000000}, 
+          {9, 100000000}, 
+          {10, 1000000000}
+      };
+    }
+    
+    @DataPoints
+    public static int[][] highestIntegers()
+    {
+      return new int[][]{
+          {1, 9}, 
+          {2, 99}, 
+          {3, 999}, 
+          {4, 9999}, 
+          {5, 99999}, 
+          {6, 999999}, 
+          {7, 9999999}, 
+          {8, 99999999}, 
+          {9, 999999999}, 
+          {10, Integer.MAX_VALUE}
+      };
+    }
+    
+    @DataPoints
+    public static int[][] randomIntegers()
+    {
+      return new int[][]{
+          {1, 1}, 
+          {2, 14}, 
+          {3, 549}, 
+          {4, 1136}, 
+          {5, 25340}, 
+          {6, 134321}, 
+          {7, 1435432}, 
+          {8, 54234129}, 
+          {9, 113683912}, 
+          {10, 1534031982}
+      };
+    }
+
+    @Theory
+    public void givenDataPoints_whenStringBasedSolutionInvoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.stringBasedSolution(entry[1]));
+    }
+
+    @Theory
+    public void givenDataPoints_whenLogarithmicApproachInvoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.logarithmicApproach(entry[1]));
+    }
+
+    @Theory
+    public void givenDataPoints_whenRepeatedMultiplicationInvoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.repeatedMultiplication(entry[1]));
+    }
+
+    @Theory
+    public void givenDataPoints_whenShiftOperatorsInvoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.shiftOperators(entry[1]));
+    }
+
+    @Theory
+    public void givenDataPoints_whenDividingWithPowersOf2Invoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.dividingWithPowersOf2(entry[1]));
+    }
+
+    @Theory
+    public void givenDataPoints_whenDivideAndConquerInvoked_thenAllPointsMatch(final int[] entry) {
+        Assume.assumeTrue(entry[0] > 0 && entry[1] > 0);
+        Assert.assertEquals(entry[0], NumberOfDigits.divideAndConquer(entry[1]));
+    }
+    
+}