java: add «206. Reverse Linked List»

Signed-off-by: Matej Focko <mfocko@redhat.com>

java/reverse-linked-list.java

@@ -0,0 +1,14 @@
+class Solution {
+  public ListNode reverseList(ListNode head) {
+    ListNode tail = null;
+
+    while (head != null) {
+      var tmp = head.next;
+      head.next = tail;
+      tail = head;
+      head = tmp;
+    }
+
+    return tail;
+  }
+}