// faster and shorter

$enum.class.getEnumConstants() :: $enum instanceof Enum =>

$enum.values()

;;

"Remove unessesary null check before instanceof.":

$a != null && $a instanceof $A =>

$a instanceof $A

;;

// shorter null check

if ($o == null) {

throw new NullPointerException($msg$);

}

=>

java.util.Objects.requireNonNull($o, $msg$);

;;

// TODO: doesn't work, jackpot ignores the body. bug?

/*

if ($o != null) {

$body$;

} else {

throw new NullPointerException($msg$);

}

=>

java.util.Objects.requireNonNull($o, $msg$);

$body$;

;;

*/

// shorter equals

$obj != null ? $obj.equals($other) : $other == null =>

java.util.Objects.equals($obj, $other)

;;

$obj != null ? !$obj.equals($other) : $other != null =>

!java.util.Objects.equals($obj, $other)

;;

($obj == $other) || ($obj != null && $obj.equals($other)) =>

java.util.Objects.equals($obj, $other)

;;

($obj != $other) || ($obj != null && !$obj.equals($other)) =>

!java.util.Objects.equals($obj, $other)

;;

// 10+

// does what it says

$o.get() :: $o instanceof java.util.Optional && sourceVersionGE(10) =>

$o.orElseThrow()

;;

// 11+

!$o.isPresent() :: $o instanceof java.util.Optional && sourceVersionGE(11) =>

$o.isEmpty()

;;

!$o.isEmpty() :: $o instanceof java.util.Optional =>

$o.isPresent()

;;

// 11+

// similar performance, strip is unicode aware, trim is not.

$str.trim() :: $str instanceof java.lang.String && sourceVersionGE(11) =>

$str.strip()

;;

// currently compiles into invokedynamic / makeConcatWithConstants

// valueOf is more direct, needs no warmup and has specialized variants.

// javac RFE https://bugs.openjdk.java.net/browse/JDK-8276951

"" + $val =>

String.valueOf($val)

;;

$val + "" =>

String.valueOf($val)

;;

$str.substring($begin, $end).indexOf($other) + $begin :: $str instanceof String && $begin instanceof int && $end instanceof int && sourceVersionGE(21) =>

$str.indexOf($other, $begin, $end)

;;

"can use formatted":

String.format($str, $args$) :: $str instanceof String && sourceVersionGE(15) =>

$str.formatted($args$)

;;

"can remove redundant toString()":

$sb1.append($sb2.toString()) :: $sb1 instanceof StringBuilder && $sb2 instanceof StringBuilder =>

$sb1.append($sb2)

;;

/* TODO: doesn't work unless there is a way to create constants

"extract Pattern constant.":

$str.matches($regex) :: $str instanceof java.lang.String && $regex instanceof java.lang.String =>

final java.util.regex.Pattern pattern = java.util.regex.Pattern.compile($regex);

pattern.matcher($str).matches()

;;

*/

// shorter toString()

$o != null ? $o.toString() : $default =>

java.util.Objects.toString($o, $default)

;;

$o == null ? $default : $o.toString() =>

java.util.Objects.toString($o, $default)

;;

System.getProperty("line.separator") =>

System.lineSeparator()

;;

System.getProperty("file.separator") =>

java.io.File.separator

;;

System.getProperty("path.separator") =>

java.io.File.pathSeparator

;;

System.getProperty("java.runtime.version") :: sourceVersionGE(9) =>

Runtime.version().toString()

;;

System.getProperty("java.specification.version") :: sourceVersionGE(10) =>

Runtime.version().feature()

;;

// no exact match unfortunately since it contains optional values

System.getProperty("java.version") :: sourceVersionGE(9) =>

Runtime.version().toString()

;;

System.getProperty("java.class.version") :: sourceVersionGE(20) =>

java.lang.reflect.ClassFileFormatVersion.latest().major()

;;

"URL.equals() resolves the host and compares the target, this is a blocking operation. Consider comparing URIs or Strings instead.":

$url1.equals($url2) :: $url1 instanceof java.net.URL && $url2 instanceof java.net.URL;;

java.util.StringJoiner $joiner = new java.util.StringJoiner($delim);

for (String $s : $iter) {

$joiner.add($s);

}

String $joined = $joiner.toString();

=>

String $joined = String.join($delim, $iter);

;;

/* todo: should be a hint but no warning

"use Long::hashCode for better hash code distribution.":

$anno$ public int hashCode() {

return (int) $id;

} :: $id instanceof long && elementKindMatches($id, ElementKind.FIELD)

=>

$anno$ public int hashCode() {

return Long.hashCode($id);

}

;;

*/

// code style

/*

for (int $i = $s; $i < $n; ++$i) {

$body$;

}

=>

for (int $i = $s; $i < $n; $i++) {

$body$;

}

;;

*/