Added surface area calculations

Author: Jaspinkl

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

@@ -149,7 +149,25 @@ public static double surfaceAreaTrapezium(final double base1, final double base2
         }
         return (base1 + base2) * height / 2;
     }
+    /**
+     * 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("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 circle.
      *