IDEA didn't use to report pointless String.substring invocations for
cases when only one character in the string is extracted. In such cases
it makes more sense to use the String#charAt method because it is
allocation free.
IDEA didn't use to suggest to refactor for the code when String.substring
selects a single character and is followed by the equals method(e.g.
args[0].substring(0, 1).equals("_")) to more readable version e.g.
args[0].charAt(0) == '_'.
This patch adds such refactorings to both of the cases. It also adds
the possiblity to handle expressions like "i+1" and "i+2" to
com.siyeh.ig.psiutils.ExpressionUtils#isDifference.
Signed-off-by: Nikita Eshkeev <nikita.eshkeev@jetbrains.com>
GitOrigin-RevId: 6d179c7c9c605f08b4d4468712f8468fd68045a1
Replaceable with append(s, x, y)
Fixes IDEA-185652 Improve StringBulder.append(s.substring(1,2)) intention
Also optimization of new expression resolution
