Add SumOfOddNumbers (#5730)

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

@@ -0,0 +1,25 @@
+package com.thealgorithms.maths;
+
+/**
+ * This program calculates the sum of the first n odd numbers.
+ *
+ * https://www.cuemath.com/algebra/sum-of-odd-numbers/
+ */
+
+public final class SumOfOddNumbers {
+    private SumOfOddNumbers() {
+    }
+
+    /**
+     * Calculate sum of the first n odd numbers
+     *
+     * @param n the number of odd numbers to sum
+     * @return sum of the first n odd numbers
+     */
+    public static int sumOfFirstNOddNumbers(final int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("n must be non-negative.");
+        }
+        return n * n;
+    }
+}