Collectors.joining() simplified [patch]

[Tomasz Linkowski]

Hi,

I found out that `Collectors.joining()` can be simplified as follows:
1) `<CharSequence, StringBuilder, String>` reduced to `<>`
2) `(r1, r2) -> { r1.append(r2); return r1; }` replaced with
`StringBuilder::append`

If such a small contribution is considered worthwhile, please sponsor it
(patch below).

Regards,
Tomasz Linkowski

PS. I've signed the OCA.



===================================================================
--- src/java.base/share/classes/java/util/stream/Collectors.java
+++ src/java.base/share/classes/java/util/stream/Collectors.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights
reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -365,9 +365,8 @@
      * {@code String}, in encounter order
      */
     public static Collector<CharSequence, ?, String> joining() {
-        return new CollectorImpl<CharSequence, StringBuilder, String>(
-                StringBuilder::new, StringBuilder::append,
-                (r1, r2) -> { r1.append(r2); return r1; },
+        return new CollectorImpl<>(
+                StringBuilder::new, StringBuilder::append,
StringBuilder::append,
                 StringBuilder::toString, CH_NOID);
     }