hg: jdk/sandbox: 8247605: Avoid array allocation when concatenating with empty string

[chris.hegarty at oracle.com]

Changeset: 66992d8c1441
Author:    tvaleev
Date:      2020-08-10 16:14 +0000
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/66992d8c1441

8247605: Avoid array allocation when concatenating with empty string
Reviewed-by: redestad, plevart

! src/java.base/share/classes/java/util/TreeMap.java
! test/jdk/java/util/Map/InPlaceOpsCollisions.java
! test/jdk/java/util/Map/MapWithCollisionsProviders.java
! test/jdk/java/util/NavigableMap/LockStep.java
! test/micro/org/openjdk/bench/java/util/TreeMapUpdate.java