Match return types for addFirst and addLast with List am: 9b651e268b am: 1f6c204bb8 am: 636ffb30f0

Original change: https://android-review.googlesource.com/c/platform/external/javaparser/+/2887806

Change-Id: I701fe7ccaa68559c0fa60478e35dfe19b34ecf49
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/javaparser-core/src/main/java/com/github/javaparser/ast/NodeList.java b/javaparser-core/src/main/java/com/github/javaparser/ast/NodeList.java
index e10e0b4..aff5964 100644
--- a/javaparser-core/src/main/java/com/github/javaparser/ast/NodeList.java
+++ b/javaparser-core/src/main/java/com/github/javaparser/ast/NodeList.java
@@ -185,17 +185,15 @@
     /**
      * Inserts the node before all other nodes.
      */
-    public NodeList<N> addFirst(N node) {
+    public void addFirst(N node) {
         add(0, node);
-        return this;
     }
 
     /**
      * Inserts the node after all other nodes. (This is simply an alias for add.)
      */
-    public NodeList<N> addLast(N node) {
+    public void addLast(N node) {
         add(node);
-        return this;
     }
 
     /**