added surface area calculation for a pyramid

src/main/java/com/thealgorithms/maths/Area.java

@@ -35,6 +35,7 @@ public static double surfaceAreaCube(final double sideLength) {
         return 6 * sideLength * sideLength;
     }
 
+
     /**
      * Calculate the surface area of a cuboid.
      *
@@ -69,24 +70,25 @@ public static double surfaceAreaSphere(final double radius) {
         return 4 * Math.PI * radius * radius;
     }
 
-    /**
-     * Calculate the surface area of a pyramid with a square base.
-     *
-     * @param sideLength side length of the square base
-     * @param slantHeight slant height of the pyramid
-     * @return surface area of the given pyramid
-     */
-    public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
-        if (sideLength <= 0) {
-            throw new IllegalArgumentException("");
-        }
-        if (slantHeight <= 0) {
-            throw new IllegalArgumentException("slant height must be greater than 0");
-        }
-        double baseArea = sideLength * sideLength;
-        double lateralSurfaceArea = 2 * sideLength * slantHeight;
-        return baseArea + lateralSurfaceArea;
-    }
+/**
+ * Calculate the surfae area of a pyramid with a square base.
+ * 
+ * @param sideLength
+ * @param slantHeight
+ * @return
+ */
+
+public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
+if (sideLength <= 0) {
+throw new IllegalArgumentException("Must be a positive sideLength");
+}
+if (slantHeight <= 0) {
+throw new IllegalArgumentException("Must be a positive slantHeight");
+}
+double baseArea = sideLength * sideLength;
+double lateralSurfaceArea = 2 * sideLength * slantHeight;
+return baseArea + lateralSurfaceArea;
+}
 
     /**
      * Calculate the area of a rectangle.