Update directory

Author: alxkm

DIRECTORY.md

@@ -431,6 +431,7 @@
             * [StrobogrammaticNumber](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/StrobogrammaticNumber.java)
             * [SumOfArithmeticSeries](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SumOfArithmeticSeries.java)
             * [SumOfDigits](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SumOfDigits.java)
+            * [SumOfOddNumbers](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SumOfOddNumbers.java)
             * [SumWithoutArithmeticOperators](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/SumWithoutArithmeticOperators.java)
             * [TrinomialTriangle](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/TrinomialTriangle.java)
             * [TwinPrime](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/maths/TwinPrime.java)
@@ -1010,6 +1011,7 @@
             * [StrobogrammaticNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/StrobogrammaticNumberTest.java)
             * [SumOfArithmeticSeriesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumOfArithmeticSeriesTest.java)
             * [SumOfDigitsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumOfDigitsTest.java)
+            * [SumOfOddNumbersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumOfOddNumbersTest.java)
             * [SumWithoutArithmeticOperatorsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/SumWithoutArithmeticOperatorsTest.java)
             * [TestArmstrong](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/TestArmstrong.java)
             * [TwinPrimeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/TwinPrimeTest.java)