Kotlin migration

Recipes for migrating to newer Kotlin versions.

Composite Recipes

Recipes that include further recipes, often including the individual recipes below.

• Migrate to Kotlin 2
• Migrate to Kotlin 2.x
• Migrate to kotlinx-datetime 0.7
• Remove redundant @OptIn annotations
• Remove redundant kotlin-stdlib dependencies
• Replace deprecated Char case conversions
• Replace deprecated String case conversions
• Replace deprecated capitalize and decapitalize
• Replace kotlinOptions with compilerOptions in Gradle build files
• Upgrade to kotlinx-coroutines 1.10
• Upgrade to kotlinx-serialization 1.8
• Use Char extensions instead of java.lang.Character
• Use Kotlin array extensions instead of java.util.Arrays
• Use Kotlin collection extensions instead of java.util.Collections
• Use Kotlin number extensions instead of java.lang.Integer/Long/Double/Float/Boolean
• Use kotlin.math instead of java.lang.Math
• Use kotlin.text.Regex instead of java.util.regex.Pattern
• Use modern Kotlin stdlib idioms

Recipes

• Remove deprecated Kotlin Gradle properties
• Rename the kotlinOptions block to compilerOptions
• Replace Enum.values() with Enum.entries
• Replace deprecated appendln with appendLine
• Replace enumValues<T>() with enumEntries<T>()
• Upgrade Kotlin Gradle plugins to 2.x
• Use ..< instead of until
• Use @JvmInline value class instead of inline class
• Use Array.contentDeepEquals() instead of Arrays.deepEquals(a, b)
• Use Array.contentDeepHashCode() instead of Arrays.deepHashCode(arr)
• Use Array.contentDeepToString() instead of Arrays.deepToString(arr)
• Use Array.contentEquals() instead of Arrays.equals(a, b)
• Use Array.contentHashCode() instead of Arrays.hashCode(arr)
• Use Array.contentToString() instead of Arrays.toString(arr)
• Use BooleanArray.contentEquals() instead of Arrays.equals(a, b)
• Use BooleanArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use BooleanArray.contentToString() instead of Arrays.toString(arr)
• Use BooleanArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use BooleanArray.fill() instead of Arrays.fill(arr, value)
• Use ByteArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use ByteArray.contentEquals() instead of Arrays.equals(a, b)
• Use ByteArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use ByteArray.contentToString() instead of Arrays.toString(arr)
• Use ByteArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use ByteArray.decodeToString() instead of String(byteArray)
• Use ByteArray.fill() instead of Arrays.fill(arr, value)
• Use ByteArray.sort() instead of Arrays.sort(arr)
• Use Char(int) instead of Int.toChar()
• Use Char.code instead of Char.toInt()
• Use Char.code.toByte() instead of Char.toByte()
• Use Char.code.toDouble() instead of Char.toDouble()
• Use Char.code.toFloat() instead of Char.toFloat()
• Use Char.code.toLong() instead of Char.toLong()
• Use Char.code.toShort() instead of Char.toShort()
• Use Char.compareTo instead of java.lang.Character.compare
• Use Char.digitToInt(radix) instead of Character.digit(c, radix)
• Use Char.isDefined() instead of Character.isDefined(c)
• Use Char.isDigit() instead of Character.isDigit(c)
• Use Char.isHighSurrogate() instead of Character.isHighSurrogate(c)
• Use Char.isISOControl() instead of Character.isISOControl(c)
• Use Char.isLetter() instead of Character.isLetter(c)
• Use Char.isLetterOrDigit() instead of Character.isLetterOrDigit(c)
• Use Char.isLowSurrogate() instead of Character.isLowSurrogate(c)
• Use Char.isLowerCase() instead of Character.isLowerCase(c)
• Use Char.isTitleCase() instead of Character.isTitleCase(c)
• Use Char.isUpperCase() instead of Character.isUpperCase(c)
• Use Char.isWhitespace() instead of Character.isWhitespace(c)
• Use Char.lowercaseChar() instead of Char.toLowerCase()
• Use Char.lowercaseChar() instead of Character.toLowerCase(c)
• Use Char.toString() instead of Character.toString(c)
• Use Char.uppercaseChar() instead of Char.toUpperCase()
• Use Char.uppercaseChar() instead of Character.toUpperCase(c)
• Use CharArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use CharArray.concatToString() instead of String(charArray)
• Use CharArray.contentEquals() instead of Arrays.equals(a, b)
• Use CharArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use CharArray.contentToString() instead of Arrays.toString(arr)
• Use CharArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use CharArray.fill() instead of Arrays.fill(arr, value)
• Use CharArray.sort() instead of Arrays.sort(arr)
• Use Collection.max() instead of Collections.max(coll)
• Use Collection.min() instead of Collections.min(coll)
• Use Double.IEEErem instead of java.lang.Math.IEEEremainder
• Use Double.nextDown() instead of java.lang.Math.nextDown
• Use Double.nextTowards() instead of java.lang.Math.nextAfter
• Use Double.nextUp() instead of java.lang.Math.nextUp
• Use Double.pow instead of java.lang.Math.pow
• Use Double.roundToLong() instead of java.lang.Math.round
• Use Double.withSign instead of java.lang.Math.copySign
• Use DoubleArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use DoubleArray.contentEquals() instead of Arrays.equals(a, b)
• Use DoubleArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use DoubleArray.contentToString() instead of Arrays.toString(arr)
• Use DoubleArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use DoubleArray.fill() instead of Arrays.fill(arr, value)
• Use DoubleArray.sort() instead of Arrays.sort(arr)
• Use Float.roundToInt() instead of java.lang.Math.round
• Use FloatArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use FloatArray.contentEquals() instead of Arrays.equals(a, b)
• Use FloatArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use FloatArray.contentToString() instead of Arrays.toString(arr)
• Use FloatArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use FloatArray.fill() instead of Arrays.fill(arr, value)
• Use FloatArray.sort() instead of Arrays.sort(arr)
• Use Int.MAX_VALUE instead of java.lang.Integer.MAX_VALUE
• Use Int.MIN_VALUE instead of java.lang.Integer.MIN_VALUE
• Use Int.compareTo instead of java.lang.Integer.compare
• Use Int.countLeadingZeroBits() instead of Integer.numberOfLeadingZeros
• Use Int.countOneBits() instead of java.lang.Integer.bitCount
• Use Int.countTrailingZeroBits() instead of Integer.numberOfTrailingZeros
• Use Int.digitToChar(radix) instead of Character.forDigit(digit, radix)
• Use Int.floorDiv instead of java.lang.Math.floorDiv
• Use Int.mod() instead of java.lang.Math.floorMod
• Use Int.rotateLeft(n) instead of Integer.rotateLeft(i, n)
• Use Int.rotateRight(n) instead of Integer.rotateRight(i, n)
• Use Int.toString() instead of Integer.toString(i)
• Use Int.toString(16) instead of Integer.toHexString
• Use Int.toString(2) instead of Integer.toBinaryString
• Use Int.toString(8) instead of Integer.toOctalString
• Use Int.toString(radix) instead of Integer.toString(i, radix)
• Use IntArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use IntArray.contentEquals() instead of Arrays.equals(a, b)
• Use IntArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use IntArray.contentToString() instead of Arrays.toString(arr)
• Use IntArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use IntArray.fill() instead of Arrays.fill(arr, value)
• Use IntArray.sort() instead of Arrays.sort(arr)
• Use Long.countOneBits() instead of java.lang.Long.bitCount
• Use Long.floorDiv instead of java.lang.Math.floorDiv
• Use Long.mod() instead of java.lang.Math.floorMod
• Use Long.mod(Int) instead of java.lang.Math.floorMod
• Use Long.rotateLeft(n) instead of Long.rotateLeft(l, n)
• Use Long.rotateRight(n) instead of Long.rotateRight(l, n)
• Use Long.toString() instead of Long.toString(l)
• Use Long.toString(radix) instead of Long.toString(l, radix)
• Use LongArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use LongArray.contentEquals() instead of Arrays.equals(a, b)
• Use LongArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use LongArray.contentToString() instead of Arrays.toString(arr)
• Use LongArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use LongArray.fill() instead of Arrays.fill(arr, value)
• Use LongArray.sort() instead of Arrays.sort(arr)
• Use MutableList.reverse() instead of Collections.reverse(list)
• Use MutableList.shuffle() instead of Collections.shuffle(list)
• Use MutableList.sort() instead of Collections.sort(list)
• Use Regex.escape(s) instead of Pattern.quote(s)
• Use ShortArray.binarySearch() instead of Arrays.binarySearch(arr, key)
• Use ShortArray.contentEquals() instead of Arrays.equals(a, b)
• Use ShortArray.contentHashCode() instead of Arrays.hashCode(arr)
• Use ShortArray.contentToString() instead of Arrays.toString(arr)
• Use ShortArray.copyOf() instead of Arrays.copyOf(arr, newLength)
• Use ShortArray.fill() instead of Arrays.fill(arr, value)
• Use ShortArray.sort() instead of Arrays.sort(arr)
• Use String.toBoolean() instead of java.lang.Boolean.parseBoolean(s)
• Use String.toDouble() instead of java.lang.Double.parseDouble(s)
• Use String.toFloat() instead of java.lang.Float.parseFloat(s)
• Use String.toInt() instead of Integer.parseInt(s)
• Use String.toInt(radix) instead of Integer.parseInt(s, radix)
• Use String.toLong() instead of java.lang.Long.parseLong(s)
• Use String.toLong(radix) instead of Long.parseLong(s, radix)
• Use String.toRegex() instead of Pattern.compile(s)
• Use Throwable.localizedMessage instead of Throwable.message
• Use appendLine() instead of appendln()
• Use appendLine(char) instead of appendln(char)
• Use appendLine(cs) instead of appendln(cs) (CharSequence)
• Use appendLine(value) instead of appendln(value)
• Use appendLine(value) instead of appendln(value) (Any?)
• Use enumEntries<T>() instead of enumValues<T>()
• Use freeCompilerArgs.addAll(...) in Kotlin compilerOptions
• Use kotlin.math.E instead of java.lang.Math.E
• Use kotlin.math.PI instead of java.lang.Math.PI
• Use kotlin.math.abs instead of java.lang.Math.abs
• Use kotlin.math.acos instead of java.lang.Math.acos
• Use kotlin.math.asin instead of java.lang.Math.asin
• Use kotlin.math.atan instead of java.lang.Math.atan
• Use kotlin.math.atan2 instead of java.lang.Math.atan2
• Use kotlin.math.cbrt instead of java.lang.Math.cbrt
• Use kotlin.math.ceil instead of java.lang.Math.ceil
• Use kotlin.math.cos instead of java.lang.Math.cos
• Use kotlin.math.cosh instead of java.lang.Math.cosh
• Use kotlin.math.exp instead of java.lang.Math.exp
• Use kotlin.math.expm1 instead of java.lang.Math.expm1
• Use kotlin.math.floor instead of java.lang.Math.floor
• Use kotlin.math.hypot instead of java.lang.Math.hypot
• Use kotlin.math.ln instead of java.lang.Math.log
• Use kotlin.math.ln1p instead of java.lang.Math.log1p
• Use kotlin.math.log10 instead of java.lang.Math.log10
• Use kotlin.math.max instead of java.lang.Math.max
• Use kotlin.math.min instead of java.lang.Math.min
• Use kotlin.math.sign instead of java.lang.Math.signum
• Use kotlin.math.sin instead of java.lang.Math.sin
• Use kotlin.math.sinh instead of java.lang.Math.sinh
• Use kotlin.math.sqrt instead of java.lang.Math.sqrt
• Use kotlin.math.tan instead of java.lang.Math.tan
• Use kotlin.math.tanh instead of java.lang.Math.tanh
• Use listOf(x) instead of Collections.singletonList(x)
• Use lowercase() instead of toLowerCase()
• Use lowercase(locale) instead of toLowerCase(locale)
• Use readln() instead of readLine()!!
• Use readlnOrNull() instead of readLine()
• Use removeAt(0) instead of removeFirst()
• Use removeAt(lastIndex) instead of removeLast()
• Use replaceFirstChar \{ it.lowercase() \} instead of decapitalize()
• Use replaceFirstChar \{ … \} instead of capitalize()
• Use setOf(x) instead of Collections.singleton(x)
• Use sumOf instead of sumBy
• Use sumOf instead of sumByDouble
• Use the jvmTarget provider syntax in Kotlin compilerOptions
• Use uppercase() instead of toUpperCase()
• Use uppercase(locale) instead of toUpperCase(locale)