hg: jdk/submit: 8240094: Optimize empty substring handling

[claes.redestad at oracle.com]

Changeset: f67951f722a4
Author:    redestad
Date:      2020-02-26 21:24 +0100
URL:       https://hg.openjdk.java.net/jdk/submit/rev/f67951f722a4

8240094: Optimize empty substring handling
Reviewed-by: redestad, igerasim, jlaskey
Contributed-by: sergei.tsypanov at yandex.ru

! src/java.base/share/classes/java/lang/String.java
! src/java.base/share/classes/java/lang/StringLatin1.java
! src/java.base/share/classes/java/lang/StringUTF16.java
! test/micro/org/openjdk/bench/java/lang/StringSubstring.java