From 3ff81a894315d4553354d40c7c6589aeb3bdc817 Mon Sep 17 00:00:00 2001
From: sampadawagde <sampada.wagde@gmail.com>
Date: Wed, 18 Mar 2020 17:13:37 +0530
Subject: [PATCH] JAVA-626 : Moved extra articles from java-math module

---
 java-math-2/README.md                         |  3 +-
 java-math-2/pom.xml                           | 14 +++++
 .../algorithms/gcd/GCDImplementation.java     | 55 +++++++++++++++++++
 .../gcd/GCDImplementationUnitTest.java        | 32 +++++++++++
 .../logarithm/LogarithmUnitTest.java          | 31 +++++++++++
 5 files changed, 134 insertions(+), 1 deletion(-)
 create mode 100644 java-math-2/src/main/java/com/baeldung/algorithms/gcd/GCDImplementation.java
 create mode 100644 java-math-2/src/test/java/com/baeldung/algorithms/gcd/GCDImplementationUnitTest.java
 create mode 100644 java-math-2/src/test/java/com/baeldung/algorithms/logarithm/LogarithmUnitTest.java

diff --git a/java-math-2/README.md b/java-math-2/README.md
index ca809e8623..5345564d5d 100644
--- a/java-math-2/README.md
+++ b/java-math-2/README.md
@@ -4,5 +4,6 @@ This module contains articles about math in Java.
 
 ### Relevant articles:
 
-- [Basic Calculator in Java](https://www.baeldung.com/basic-calculator-in-java)
+- [Calculating Logarithms in Java](https://www.baeldung.com/java-logarithms)
+- [Finding Greatest Common Divisor in Java](https://www.baeldung.com/java-greatest-common-divisor)
 - More articles: [[<-- prev]](/../java-math)
diff --git a/java-math-2/pom.xml b/java-math-2/pom.xml
index e22dcc2b31..7bc05a3a86 100644
--- a/java-math-2/pom.xml
+++ b/java-math-2/pom.xml
@@ -12,4 +12,18 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    
+    </dependencies>
+    
+    <properties>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+    </properties>
+  
 </project>
\ No newline at end of file
diff --git a/java-math-2/src/main/java/com/baeldung/algorithms/gcd/GCDImplementation.java b/java-math-2/src/main/java/com/baeldung/algorithms/gcd/GCDImplementation.java
new file mode 100644
index 0000000000..d4844abd9c
--- /dev/null
+++ b/java-math-2/src/main/java/com/baeldung/algorithms/gcd/GCDImplementation.java
@@ -0,0 +1,55 @@
+package com.baeldung.algorithms.gcd;
+
+public class GCDImplementation {
+
+    public static int gcdByBruteForce(int n1, int n2) {
+        int gcd = 1;
+        for (int i = 1; i <= n1 && i <= n2; i++) {
+            if (n1 % i == 0 && n2 % i == 0) {
+                gcd = i;
+            }
+        }
+        return gcd;
+    }
+
+    public static int gcdByEuclidsAlgorithm(int n1, int n2) {
+        if (n2 == 0) {
+            return n1;
+        }
+        return gcdByEuclidsAlgorithm(n2, n1 % n2);
+    }
+
+    public static int gcdBySteinsAlgorithm(int n1, int n2) {
+        if (n1 == 0) {
+            return n2;
+        }
+
+        if (n2 == 0) {
+            return n1;
+        }
+
+        int n;
+        for (n = 0; ((n1 | n2) & 1) == 0; n++) {
+            n1 >>= 1;
+            n2 >>= 1;
+        }
+
+        while ((n1 & 1) == 0) {
+            n1 >>= 1;
+        }
+
+        do {
+            while ((n2 & 1) == 0) {
+                n2 >>= 1;
+            }
+
+            if (n1 > n2) {
+                int temp = n1;
+                n1 = n2;
+                n2 = temp;
+            }
+            n2 = (n2 - n1);
+        } while (n2 != 0);
+        return n1 << n;
+    }
+}
diff --git a/java-math-2/src/test/java/com/baeldung/algorithms/gcd/GCDImplementationUnitTest.java b/java-math-2/src/test/java/com/baeldung/algorithms/gcd/GCDImplementationUnitTest.java
new file mode 100644
index 0000000000..d2c91a2eb8
--- /dev/null
+++ b/java-math-2/src/test/java/com/baeldung/algorithms/gcd/GCDImplementationUnitTest.java
@@ -0,0 +1,32 @@
+package com.baeldung.algorithms.gcd;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class GCDImplementationUnitTest {
+
+    @Test
+    public void whenCalculatingGCDByBruteForceMethod_thenCorrect() {
+        int n1 = 60;
+        int n2 = 90;
+        int gcd = GCDImplementation.gcdByBruteForce(n1, n2);
+        assertThat(gcd).isEqualTo(30);
+    }
+
+    @Test
+    public void whenCalculatingGCDByEuclidsAlgorithm_thenCorrect() {
+        int n1 = 60;
+        int n2 = 90;
+        int gcd = GCDImplementation.gcdByEuclidsAlgorithm(n1, n2);
+        assertThat(gcd).isEqualTo(30);
+    }
+
+    @Test
+    public void whenCalculatingGCDBySteinsAlgorithm_thenCorrect() {
+        int n1 = 60;
+        int n2 = 90;
+        int gcd = GCDImplementation.gcdBySteinsAlgorithm(n1, n2);
+        assertThat(gcd).isEqualTo(30);
+    }
+}
diff --git a/java-math-2/src/test/java/com/baeldung/algorithms/logarithm/LogarithmUnitTest.java b/java-math-2/src/test/java/com/baeldung/algorithms/logarithm/LogarithmUnitTest.java
new file mode 100644
index 0000000000..facad1edc4
--- /dev/null
+++ b/java-math-2/src/test/java/com/baeldung/algorithms/logarithm/LogarithmUnitTest.java
@@ -0,0 +1,31 @@
+package com.baeldung.algorithms.logarithm;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.Test;
+
+public class LogarithmUnitTest {
+
+    @Test
+    public void givenLog10_shouldReturnValidResults() {
+        assertEquals(Math.log10(100), 2);
+        assertEquals(Math.log10(1000), 3);
+    }
+
+    @Test
+    public void givenLogE_shouldReturnValidResults() {
+        assertEquals(Math.log(Math.E), 1);
+        assertEquals(Math.log(10), 2.30258, 0.00001);
+    }
+
+    @Test
+    public void givenCustomLog_shouldReturnValidResults() {
+        assertEquals(customLog(2, 256), 8);
+        assertEquals(customLog(10, 100), 2);
+    }
+
+    private static double customLog(double base, double logNumber) {
+        return Math.log(logNumber) / Math.log(base);
+    }
+
+}