New checks:

• ExplicitArrayForVarargs: discourage unnecessary explicit construction of an array to provide varargs.
• FloggerPerWithoutRateLimit: discourage Flogger's perUnique without rate limiting
• StringJoin: Ban String.join(CharSequence) and String.join(CharSequence, CharSequence)
• ThreadBuilderNameWithPlaceholder: Do not allow placeholders in Thread.Builder.name(String) or name(String, int).

Changes:

• The return type of ASTHelpers.asFlagSet has changed. The previous type was EnumSet<Flags.Flag>, where Flags.Flag is an enum in the javac class Flags. A recent JDK change has replaced that enum with a new top-level enum called FlagsEnum. It is not possible to change ASTHelpers.asFlagSet in a way that would be type-safe and compatible with the enums from JDKs both before and after the change. Instead, the method now returns ImmutableSet<String>, where the strings come from the toString() of the enum constants. That means they are "native", "abstract", etc.
• Flag IO.print[ln]() in SystemOut.

Full changelog: v2.41.0...v2.42.0