implement generateTriangle method

src/main/java/MainExercises.java

@@ -20,9 +20,20 @@ public class MainExercises
  */
     public char[][] generateTriangle(int n) {
 
-        // todo
-        return null;
+        char[][] triangle = new char[n][];
 
+        for (int i=0 ; i<n ; i++) {
+
+            triangle[i] = new char[i+1];
+            for(int j=0 ; j<=i ; j++) {
+
+                if (j == 0 || j == i || i == n-1)
+                    triangle[i][j] = '*';
+                else
+                    triangle[i][j] = ' ';
+            }
+        }
+        return triangle;
     }