feat: adds David Smith Java Leetcode for Lesson 11

lesson_11/arrays_java/arrays_app/src/main/java/com/codedifferently/lesson11/Lesson11.java

@@ -1,5 +1,6 @@
 package com.codedifferently.lesson11;
 
+import java.util.ArrayList;
 import java.util.List;
 
 public class Lesson11 {
@@ -9,14 +10,24 @@ public class Lesson11 {
    * https://leetcode.com/problems/concatenation-of-array
    */
   public int[] getConcatenation(int[] nums) {
-    return null;
+    int n = nums.length;
+    int[] ans = new int[2 * n]; 
+    System.arraycopy(nums, 0, ans, 0, n);
+    System.arraycopy(nums, 0, ans, n, n);
+    return ans;
   }
 
   /**
    * Provide the solution to LeetCode 2942 here:
    * https://leetcode.com/problems/find-words-containing-character/
    */
   public List<Integer> findWordsContaining(String[] words, char x) {
-    return null;
+        List<Integer> result = new ArrayList<>();
+                for (int i = 0; i < words.length; i++) {
+            if (words[i].indexOf(x) != -1) {
+                result.add(i);
+            }
+        }
+        return result;
+    }
   }
-}