BAEL-5385 Code for Automorphic Number. (#11928)

java-numbers-4/src/main/java/com/baeldung/automorphicnumber/AutomorphicNumber.java

@@ -0,0 +1,31 @@
+package com.baeldung.automorphicnumber;
+
+public class AutomorphicNumber {
+
+    public static void main(String[] args) {
+        System.out.println(isAutomorphicUsingLoop(76));
+        System.out.println(isAutomorphicUsingMath(76));
+    }
+
+    public static boolean isAutomorphicUsingMath(int number) {
+        int square = number * number;
+
+        int numberOfDigits = (int) Math.floor(Math.log10(number) + 1);
+        int lastDigits = (int) (square % (Math.pow(10, numberOfDigits)));
+
+        return number == lastDigits;
+    }
+
+    public static boolean isAutomorphicUsingLoop(int number) {
+        int square = number * number;
+
+        while (number > 0) {
+            if (number % 10 != square % 10) {
+                return false;
+            }
+            number /= 10;
+            square /= 10;
+        }
+        return true;
+    }
+}

java-numbers-4/src/test/java/com/baeldung/automorphicnumber/AutomorphicNumberUnitTest.java

@@ -0,0 +1,19 @@
+package com.baeldung.automorphicnumber;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+public class AutomorphicNumberUnitTest {
+
+    @Test
+    void givenANumber_whenPassed_thenShouldDetermineAutomorphicOrNot() {
+        int number1 = 76; // automorphic
+        int number2 = 16; // not automorphic 
+        assertTrue(AutomorphicNumber.isAutomorphicUsingLoop(number1));
+        assertFalse(AutomorphicNumber.isAutomorphicUsingLoop(number2));
+        assertTrue(AutomorphicNumber.isAutomorphicUsingMath(number1));
+        assertFalse(AutomorphicNumber.isAutomorphicUsingMath(number2));
+    }
+}