Update directory

Author: Hardvan

DIRECTORY.md

@@ -239,6 +239,7 @@
             * [KnapsackMemoization](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/KnapsackMemoization.java)
             * [LevenshteinDistance](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LevenshteinDistance.java)
             * [LongestAlternatingSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LongestAlternatingSubsequence.java)
+            * [LongestArithmeticSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LongestArithmeticSubsequence.java)
             * [LongestCommonSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LongestCommonSubsequence.java)
             * [LongestIncreasingSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LongestIncreasingSubsequence.java)
             * [LongestPalindromicSubsequence](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubsequence.java)
@@ -735,6 +736,7 @@
             * [KnapsackTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/KnapsackTest.java)
             * [LevenshteinDistanceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LevenshteinDistanceTests.java)
             * [LongestAlternatingSubsequenceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestAlternatingSubsequenceTest.java)
+            * [LongestArithmeticSubsequenceTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestArithmeticSubsequenceTest.java)
             * [LongestIncreasingSubsequenceTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestIncreasingSubsequenceTests.java)
             * [LongestPalindromicSubstringTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java)
             * [LongestValidParenthesesTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/LongestValidParenthesesTest.java)