More examples

build.gradle

@@ -22,7 +22,7 @@ repositories {
 
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlin_version"
-    testCompile group: 'junit', name: 'junit', version: '4.12'
+    compile group: 'junit', name: 'junit', version: '4.12'
 }
 
 compileKotlin {

src/main/kotlin/t01_SmallClasses/bad/Address.kt

@@ -0,0 +1,4 @@
+package t01_SmallClasses.bad
+
+class Address(val city: String, val street: String, val zipCode: String) {
+}

src/main/kotlin/t01_SmallClasses/bad/Company.kt

@@ -0,0 +1,4 @@
+package t01_SmallClasses.bad
+
+class Company(val personnel: List<Person>, val address: Address) {
+}

src/main/kotlin/t01_SmallClasses/bad/Person.kt

@@ -0,0 +1,4 @@
+package t01_SmallClasses.bad
+
+class Person(val name: String, val address: Address) {
+}

src/main/kotlin/t01_SmallClasses/good.kt

@@ -0,0 +1,7 @@
+package t01_SmallClasses
+
+class Address(val city: String, val street: String, val zipCode: String)
+
+class Person(val name: String, val address: Address)
+
+class Company(val personnel: List<Person>, val address: Address)

src/main/kotlin/t03_Lateinit/bad.kt

@@ -0,0 +1,19 @@
+package t03_Lateinit.bad
+
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Test
+
+class MyTest {
+    class State(val data: String)
+
+    private var state: State? = null
+
+    @Before fun setup() {
+        state = State("abc")
+    }
+
+    @Test fun foo() {
+        Assert.assertEquals("abc", state!!.data)
+    }
+}

src/main/kotlin/t03_Lateinit/good.kt

@@ -0,0 +1,19 @@
+package t03_Lateinit.good
+
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Test
+
+class MyTest {
+    class State(val data: String)
+
+    private lateinit var state: State
+
+    @Before fun setup() {
+        state = State("abc")
+    }
+
+    @Test fun foo() {
+        Assert.assertEquals("abc", state.data)
+    }
+}

src/main/kotlin/t04_Typealias/bad.kt

@@ -0,0 +1,11 @@
+package t04_Typealias.bad
+
+class Event
+
+class HandlerList {
+    fun addOnClickHandler(handler: (Event) -> Unit) {
+    }
+
+    fun removeOnClickHandler(handler: (Event) -> Unit) {
+    }
+}

src/main/kotlin/t04_Typealias/good.kt

@@ -0,0 +1,11 @@
+package t04_Typealias.good
+
+class Event
+
+class HandlerList {
+    fun addOnClickHandler(handler: (Event) -> Unit) {
+    }
+
+    fun removeOnClickHandler(handler: (Event) -> Unit) {
+    }
+}

src/main/kotlin/t05_ToplevelFunctions/bad.kt

@@ -0,0 +1,7 @@
+package t05_ToplevelFunctions.bad
+
+class StringUtils {
+    companion object {
+        fun isPhoneNumber(s: String) = s.length == 7 && s.all { it.isDigit() }
+    }
+}

src/main/kotlin/t05_ToplevelFunctions/good.kt

@@ -0,0 +1,3 @@
+package t05_ToplevelFunctions.bad
+
+fun isPhoneNumber(s: String) = s.length == 7 && s.all { it.isDigit() }

src/main/kotlin/t06_ExtensionFunctions/bad.kt

@@ -0,0 +1,3 @@
+package t06_ExtensionFunctions.bad
+
+fun isPhoneNumber(s: String) = s.length == 7 && s.all { it.isDigit() }

src/main/kotlin/t06_ExtensionFunctions/good.kt

@@ -0,0 +1,3 @@
+package t06_ExtensionFunctions.good
+
+fun String.isPhoneNumber() = length == 7 && all { it.isDigit() }

src/main/kotlin/t07_MemberExtensionFunctions/bad.kt

@@ -0,0 +1,7 @@
+package t07_MemberExtensionFunctions.bad
+
+class PhoneBook {
+    fun String.isPhoneNumber() = length == 7 && all { it.isDigit() }
+
+    fun PhoneBook.findPhone(name: String) = "1234567"
+}

src/main/kotlin/t07_MemberExtensionFunctions/good.kt

@@ -0,0 +1,7 @@
+package t07_MemberExtensionFunctions.good
+
+class PhoneBook {
+    fun findPhone(name: String) = "1234567"
+}
+
+private fun String.isPhoneNumber() = length == 7 && all { it.isDigit() }

src/main/kotlin/t08_ExtensionFunctionsAPI/bad.kt

@@ -0,0 +1,6 @@
+package t07_MemberExtensionFunctions.bad
+
+class Person(val firstName: String, val lastName: String) {
+    val fullName: String
+        get() = "$firstName $lastName"
+}

src/main/kotlin/t08_ExtensionFunctionsAPI/good.kt

@@ -0,0 +1,7 @@
+package t07_MemberExtensionFunctions.good
+
+class Person(val firstName: String, val lastName: String) {
+}
+
+val Person.fullName: String
+    get() = "$firstName $lastName"

src/main/kotlin/t09_OmitReturnTypes/IJavaInterface.java

@@ -0,0 +1,8 @@
+package t09_OmitReturnTypes;
+
+/**
+ * @author yole
+ */
+public interface IJavaInterface {
+    String getJavaValue();
+}

src/main/kotlin/t09_OmitReturnTypes/bad.kt

@@ -0,0 +1,9 @@
+package t09_OmitReturnTypes.bad
+
+import t09_OmitReturnTypes.IJavaInterface
+
+class KtImpl : IJavaInterface {
+    fun getName(): String = "Foo"
+
+    override fun getJavaValue() = System.getProperty("java.value")
+}

src/main/kotlin/t09_OmitReturnTypes/good.kt

@@ -0,0 +1,9 @@
+package t09_OmitReturnTypes.good
+
+import t09_OmitReturnTypes.IJavaInterface
+
+class KtImpl : IJavaInterface {
+    fun getName() = "Foo"
+
+    override fun getJavaValue(): String? = System.getProperty("java.value")
+}

src/main/kotlin/t10_Overloads/bad.kt

@@ -0,0 +1,14 @@
+package t10_Overloads.bad
+
+class Phonebook {
+    fun print() {
+        print(",")
+    }
+
+    fun print(columnSeparator: String) {
+    }
+}
+
+fun main(args: Array<String>) {
+    Phonebook().print("|")
+}

src/main/kotlin/t10_Overloads/good.kt

@@ -0,0 +1,13 @@
+package t10_Overloads.good
+
+import t10_Overloads.bad.Phonebook
+
+class Phonebook {
+    fun print(columnSeparator: String = ",") {
+    }
+}
+
+fun main(args: Array<String>) {
+    Phonebook().print(columnSeparator = "|")
+}
+

src/main/kotlin/t11_ReturnMultipleValues/bad.kt

@@ -0,0 +1,9 @@
+package t11_ReturnMultipleValues.bad
+
+fun returnMultipleValues(): Pair<Int, String> = 1 to "one"
+
+fun main(args: Array<String>) {
+    val pair = returnMultipleValues()
+    val number = pair.first
+    val name = pair.second
+}

src/main/kotlin/t11_ReturnMultipleValues/good.kt

@@ -0,0 +1,9 @@
+package t11_ReturnMultipleValues.good
+
+data class NamedNumber(val number: Int, val name: String)
+
+fun returnMultipleValues() = NamedNumber(1, "one")
+
+fun main(args: Array<String>) {
+    val (number, name) = returnMultipleValues()
+}

src/main/kotlin/t12_DestructuringList/bad.kt

@@ -0,0 +1,11 @@
+package t12_DestructuringList.bad
+
+data class NameComponents(val name: String, val ext: String?)
+
+fun splitNameAndExtension(filename: String): NameComponents {
+    if ('.' in filename) {
+        val parts = filename.split('.', limit = 2)
+        return NameComponents(parts[0], parts[1])
+    }
+    return NameComponents(filename, null)
+}

src/main/kotlin/t12_DestructuringList/good.kt

@@ -0,0 +1,11 @@
+package t12_DestructuringList.good
+
+data class NameComponents(val name: String, val ext: String?)
+
+fun splitNameAndExtension(filename: String): NameComponents {
+    if ('.' in filename) {
+        val (name, ext) = filename.split('.', limit = 2)
+        return NameComponents(name, ext)
+    }
+    return NameComponents(filename, null)
+}

src/main/kotlin/t13_WhenAsExpressionBody/bad.kt

@@ -0,0 +1,9 @@
+package t13_WhenAsExpressionBody.bad
+
+fun parseEnglishNumber(number: String): Int? {
+    when (number) {
+        "one" -> return 1
+        "two" -> return 2
+        else -> return null
+    }
+}

src/main/kotlin/t13_WhenAsExpressionBody/good.kt

@@ -0,0 +1,7 @@
+package t13_WhenAsExpressionBody.good
+
+fun parseEnglishNumber(number: String) = when (number) {
+    "one" -> 1
+    "two" -> 2
+    else -> null
+}

src/main/kotlin/t14_TryAsExpressionBody/bad.kt

@@ -0,0 +1,10 @@
+package t14_TryAsExpressionBody.bad
+
+fun tryParseInt(number: String): Int? {
+    try {
+        return Integer.parseInt(number)
+    }
+    catch (e: NumberFormatException) {
+        return null
+    }
+}

src/main/kotlin/t14_TryAsExpressionBody/good.kt

@@ -0,0 +1,9 @@
+package t14_TryAsExpressionBody.good
+
+fun tryParseInt(number: String) =
+    try {
+        Integer.parseInt(number)
+    }
+    catch (e: NumberFormatException) {
+        null
+    }

src/main/kotlin/t15_ReturnInElvis/bad.kt

@@ -0,0 +1,12 @@
+package t15_ReturnInElvis.bad
+
+class Person(val name: String?, val age: Int?)
+
+fun processPerson(person: Person) {
+    if (person.name == null)
+        throw IllegalArgumentException("Person must have a name")
+    if (person.age == null) return
+
+    println("${person.name}: ${person.age}")
+}
+

src/main/kotlin/t15_ReturnInElvis/good.kt

@@ -0,0 +1,11 @@
+package t15_ReturnInElvis.good
+
+class Person(val name: String?, val age: Int?)
+
+fun processPerson(person: Person) {
+    val name = person.name ?:
+            throw IllegalArgumentException("Person must have a name")
+    val age = person.age ?: return
+
+    println("$name: $age")
+}

src/main/kotlin/t16_Range/bad.kt

@@ -0,0 +1,3 @@
+package t16_Range.bad
+
+fun isLatinUppercase(c: Char) = c >= 'A' && c <= 'Z'

src/main/kotlin/t16_Range/good.kt

@@ -0,0 +1,3 @@
+package t16_Range.good
+
+fun isLatinUppercase(c: Char) = c in 'A'..'Z'

src/main/kotlin/t17_CoerceIn/bad.kt

@@ -0,0 +1,9 @@
+package t17_CoerceIn.bad
+
+fun updateProgress(value: Int) {
+    val actualValue = when {
+        value < 0   -> 0
+        value > 100 -> 100
+        else        -> value
+    }
+}

src/main/kotlin/t17_CoerceIn/good.kt

@@ -0,0 +1,5 @@
+package t17_CoerceIn.good
+
+fun updateProgress(value: Int) {
+    val actualValue = value.coerceIn(0, 100)
+}

src/main/kotlin/t18_DestructuringInLoops/bad.kt

@@ -0,0 +1,7 @@
+package t18_DestructuringInLoops.bad
+
+fun printMap(map: Map<String, String>) {
+    for (item in map.entries) {
+        println("${item.key} -> ${item.value}")
+    }
+}

src/main/kotlin/t18_DestructuringInLoops/good.kt

@@ -0,0 +1,7 @@
+package t18_DestructuringInLoops.good
+
+fun printMap(map: Map<String, String>) {
+    for ((key, value) in map) {
+        println("$key -> $value")
+    }
+}

src/main/kotlin/t19_Optional/bad.kt

@@ -0,0 +1,8 @@
+package t19_Optional.bad
+
+import java.util.*
+
+fun processOptional(x: Optional<String>) {
+    val s = x.orElse("Unknown")
+    val firstChar = x.flatMap { Optional.ofNullable(it.firstOrNull()) }
+}

src/main/kotlin/t19_Optional/good.kt

@@ -0,0 +1,6 @@
+package t19_Optional.good
+
+fun processOptional(x: String?) {
+    val s = x ?: "Unknown"
+    val firstChar = x?.firstOrNull()
+}