From 9dae389faa03b8400b6f0796383f47495887151a Mon Sep 17 00:00:00 2001
From: Appari Satya Barghav <36763910+satyabarghav@users.noreply.github.com>
Date: Tue, 24 Oct 2023 02:39:42 +0530
Subject: [PATCH] Herons : Changed the signature of the function (#4686)

* Made changes to the code to correct the Logic of Armstrong Number

* Resolved the issues

* Trying to resolve the Linter error by changing Variable name

* Changed Variable Names : trying to resolve Clang error

* Chnged the signature of the function

* Added the Function documentation

* Added exception for parameters

* Resolved with suggested changes

* Resolved with Suggested changes

* fix: use proper logic

---------

Co-authored-by: vil02 <vil02@o2.pl>
---
 .../thealgorithms/maths/HeronsFormula.java    | 35 ++++++++++++++-----
 .../maths/HeronsFormulaTest.java              | 20 ++++++++---
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/src/main/java/com/thealgorithms/maths/HeronsFormula.java b/src/main/java/com/thealgorithms/maths/HeronsFormula.java
index 72052a1b8..5baee715d 100644
--- a/src/main/java/com/thealgorithms/maths/HeronsFormula.java
+++ b/src/main/java/com/thealgorithms/maths/HeronsFormula.java
@@ -1,18 +1,35 @@
 package com.thealgorithms.maths;
 
 /**
+ * Wikipedia for HeronsFormula => https://en.wikipedia.org/wiki/Heron%27s_formula
  * Find the area of a triangle using only side lengths
  */
 
-public class HeronsFormula {
+public final class HeronsFormula {
 
-    public static double Herons(int s1, int s2, int s3) {
-        double a = s1;
-        double b = s2;
-        double c = s3;
-        double s = (a + b + c) / 2.0;
-        double area = 0;
-        area = Math.sqrt((s) * (s - a) * (s - b) * (s - c));
-        return area;
+    /*
+     * A function to get the Area of a Triangle using Heron's Formula
+     * @param s1,s2,s3 => the three sides of the Triangle
+     * @return area using the formula (√(s(s – s1)(s – s2)(s – s3)))
+     * here s is called semi-perimeter and it is the half of the perimeter (i.e; s = (s1+s2+s3)/2)
+     * @author satyabarghav
+     */
+    private HeronsFormula() {
+    }
+
+    private static boolean areAllSidesPositive(final double a, final double b, final double c) {
+        return a > 0 && b > 0 && c > 0;
+    }
+
+    private static boolean canFormTriangle(final double a, final double b, final double c) {
+        return a + b > c && b + c > a && c + a > b;
+    }
+
+    public static double herons(final double a, final double b, final double c) {
+        if (!areAllSidesPositive(a, b, c) || !canFormTriangle(a, b, c)) {
+            throw new IllegalArgumentException("Triangle can't be formed with the given side lengths");
+        }
+        final double s = (a + b + c) / 2.0;
+        return Math.sqrt((s) * (s - a) * (s - b) * (s - c));
     }
 }
diff --git a/src/test/java/com/thealgorithms/maths/HeronsFormulaTest.java b/src/test/java/com/thealgorithms/maths/HeronsFormulaTest.java
index 32feeacdb..22cecf4dc 100644
--- a/src/test/java/com/thealgorithms/maths/HeronsFormulaTest.java
+++ b/src/test/java/com/thealgorithms/maths/HeronsFormulaTest.java
@@ -7,21 +7,33 @@ public class HeronsFormulaTest {
 
     @Test
     void test1() {
-        Assertions.assertEquals(HeronsFormula.Herons(3, 4, 5), 6.0);
+        Assertions.assertEquals(HeronsFormula.herons(3, 4, 5), 6.0);
     }
 
     @Test
     void test2() {
-        Assertions.assertEquals(HeronsFormula.Herons(24, 30, 18), 216.0);
+        Assertions.assertEquals(HeronsFormula.herons(24, 30, 18), 216.0);
     }
 
     @Test
     void test3() {
-        Assertions.assertEquals(HeronsFormula.Herons(1, 1, 1), 0.4330127018922193);
+        Assertions.assertEquals(HeronsFormula.herons(1, 1, 1), 0.4330127018922193);
     }
 
     @Test
     void test4() {
-        Assertions.assertEquals(HeronsFormula.Herons(4, 5, 8), 8.181534085976786);
+        Assertions.assertEquals(HeronsFormula.herons(4, 5, 8), 8.181534085976786);
+    }
+
+    @Test
+    public void testCalculateAreaWithInvalidInput() {
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(1, 2, 3); });
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(2, 1, 3); });
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(3, 2, 1); });
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(1, 3, 2); });
+
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(1, 1, 0); });
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(1, 0, 1); });
+        Assertions.assertThrows(IllegalArgumentException.class, () -> { HeronsFormula.herons(0, 1, 1); });
     }
 }