Kotlin

Transcript

7. val firstName: String = "Drew" val lastName: String? = null
8. val firstName: String = "Drew" val lastName: String? = null
9. val firstName: String = "Drew" val lastName: String? = null
10. val firstName: String = "Drew" val lastName: String? = null
11. val firstName: String = "Drew" val lastName: String? = null
12. val firstName = "Drew" val lastName: String? = null
13. fun sum(a: Int, b: Int): Int { return a + b }
14. fun sum(a: Int, b: Int): Int { return a + b }
15. fun sum(a: Int, b: Int): Int { return a + b }
16. fun sum(a: Int, b: Int): Int { return a + b }
17. fun sum(a: Int, b: Int): Int = a + b
18. fun sum(a: Int, b: Int): Int = a + b
19. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default }
20. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default }
21. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default }
22. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default }
23. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default } stringOrDefault(name)
24. fun sum(a: Int, b: Int): Int = a + b fun stringOrDefault( subject: String?, default: String = "Default" ): String { return subject "?: default } stringOrDefault(name) stringOrDefault(name, "missing")
25. "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
26. "// Kotlin val user = User() println("User: " + user.name) "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
27. "// Kotlin val user = User() println("User: " + user.name) "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
28. "// Kotlin val user = User() println("User: " + user.name) user.name = "Not Drew" "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
29. "// Kotlin val user = User() println("User: " + user.name) user.name = "Not Drew" "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
30. "// Kotlin val user = User() println("User: ${user.name}") user.name = "Not Drew" "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
31. "// Kotlin val user = User() println("User: $user") user.name = "Not Drew" "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
32. "// Kotlin val user = User() println("User: $user") user.name = "Not Drew" "// Java public class User { @NonNull public String getName() { "// ""... } public void setName(@NonNull String name) { "// ""... } }
33. "// Kotlin class User { var name = "Drew" }
34. "// Kotlin class User { var name = "Drew" }
35. "// Java final User user = new User(); System.out.println("User: " + user.getName()); "// Kotlin class User { var name = "Drew" }
36. "// Java final User user = new User(); System.out.println("User: " + user.getName()); "// Kotlin class User { var name = "Drew" }
37. "// Java final User user = new User(); System.out.println("User: " + user.getName()); user.setName("Not Drew"); "// Kotlin class User { var name = "Drew" }
38. "// Java final User user = new User(); System.out.println("User: " + user.getName()); user.setName("Not Drew"); "// Kotlin class User { var name = "Drew" }
39. "// Kotlin val user = User()
40. "// Kotlin val user = User() user = User()
41. var currentUser = User() currentUser = User() "// Kotlin val user = User() user = User()
42. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language }
43. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language }
44. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language }
45. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language } val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { println("The Locale's language is English.") } else { println("The Locale's language is not english") }
46. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language } val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { println("The Locale's language is English.") } else { println("The Locale's language is not english") }
47. "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language } import com.app.isLanguageEnglish val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { println("The Locale's language is English.") } else { println("The Locale's language is not english") }
48. "// Java LocaleKt.isLanguageEnglish(Locale.UK); val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { "//""... } "// Kotlin "// file: com/app/locale.kt fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language }
49. "// Kotlin "// file: com/app/locale.kt @file:JvmName("LocaleUtils") fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language } val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { "//""... } "// Java LocaleKt.isLanguageEnglish(Locale.UK);
50. "// Kotlin "// file: com/app/locale.kt @file:JvmName("LocaleUtils") fun Locale.isLanguageEnglish(): Boolean { return language "== Locale.ENGLISH.language } val locale = Locale.GERMANY if (locale.isLanguageEnglish()) { "//""... } "// Java LocaleUtils.isLanguageEnglish(Locale.UK);
51. val executor = Executors.newCachedThreadPool() executor.execute { println("from the background") }
52. val executor = Executors.newCachedThreadPool() executor.execute { println("from the background") }
53. val worker = Worker() val executor = Executors.newCachedThreadPool() executor.execute(worker"::doWork) class Worker { fun doWork() { println("from the background") } }
54. val worker = Worker() val executor = Executors.newCachedThreadPool() executor.execute(worker"::doWork) class Worker { fun doWork() { println("from the background") } }
55. val work = { println("from the background") } val executor = Executors.newCachedThreadPool() executor.execute(work)
56. val work = { println("from the background") } val executor = Executors.newCachedThreadPool() executor.execute(work)
57. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... }
58. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... }
59. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val names = listOf("Drew", "Ahsan", "Shivangi") val drews = names.filter({ name !-> name "== "Drew" })
60. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter({ name !-> name "== "Drew" }) val names = listOf("Drew", "Ahsan", "Shivangi")
61. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter({ it "== "Drew" }) val names = listOf("Drew", "Ahsan", "Shivangi")
62. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter() { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi")
63. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi")
64. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi") val ahsans = names.filterTo(mutableSetOf()) { it == "Ahsan" }
65. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi") val ahsans = names.filterTo(mutableSetOf()) { it == "Ahsan" }
66. fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... } val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi") val ahsans = names.filterTo(mutableSetOf()) { it == "Ahsan" }
67. val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi") fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... }
68. val drews = names.filter { it "== "Drew" } val names = listOf("Drew", "Ahsan", "Shivangi") inline fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { "// ""... }
69. inline fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { val destination = mutableListOf<T>() for (item in this) { if (predicate(item)) destination.add(item) } return destination } val names = listOf("Drew", "Ahsan", "Shivangi") val drews = names.filter { it "== "Drew" }
70. inline fun <T> List<T>.filter(predicate: (T) "-> Boolean): List<T> { val destination = mutableListOf<T>() for (item in this) { if (predicate(item)) destination.add(item) } return destination } val destination = mutableListOf<String>() for (item in names) { if (item "== "Drew") destination.add(item) } val drews: List<String> = destination
71. class User { val name = "drew" }
72. class User(name: String) { val name = name }
73. class User(val name: String) { }
74. class User(val name: String)
75. class User(val name: String) val drew = User("Drew") println("Hello, $drew")
76. class User(val name: String) val drew = User("Drew") println("Hello, $drew") Hello, User@8c64f2bc
77. class User(val name: String) val drew = User("Drew") println("Hello, $drew") Hello, User@8c64f2bc
78. data class User(val name: String) val drew = User("Drew") println("Hello, $drew") Hello, User@8c64f2bc
79. data class User(val name: String) val drew = User("Drew") println("Hello, $drew") Hello, User(name=Drew)
80. data class User(val name: String) val drew = User("Drew") println("Hello, $drew") Hello, User(name=Drew)
81. data class User(val name: String, val age: Int) val drew = User("Drew", 5)
82. data class User(val name: String, val age: Int) val drew = User("Drew", 5)
83. data class User(val name: String, val age: Int) val drew = User("Drew", 5) val updated = drew.copy(age = 6)
84. data class User(val name: String, val age: Int) val drew = User("Drew", 5)
85. data class User(val name: String, val age: Int) val drew = User("Drew", 5) val (name, age) = drew
86. data class User(val name: String, val age: Int) val drew = User("Drew", 5) val (name, age) = drew val (key, value) = Pair("session_id", "1")
87. data class User(val name: String, val age: Int) val drew = User("Drew", 5) val (name, age) = drew val (key, value) = Pair("session_id", "1") val (x, y, z) = Triple(0f, 0f, 1f)
88. data class User(val name: String, val age: Int) val drew = User("Drew", 5) val (name, age) = drew val (key, value) = Pair("session_id", "1") val (x, y, z) = Triple(0f, 0f, 1f)
89. enum class Result { SUCCESS, ERROR, }
90. enum class Result { SUCCESS, ERROR(val exception: Exception), }
91. sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
92. sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
93. sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
94. sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
95. sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
96. // otherfile.kt class ExternalResult<out T : Any> : Result<T>() sealed class Result<T> { class Success<T> : Result<T>() class Error : Result<Nothing>() }
97. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() } // otherfile.kt class ExternalResult<out T : Any> : Result<T>()
98. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() }
99. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() } fun handleResult(result: Result<String>) { when (result) { is Result.Success -> TODO("handle") is Result.Error -> TODO("handle") } }
100. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() } fun handleResult(result: Result<String>) { when (result) { is Result.Success -> result.data is Result.Error -> result.exception.message } }
101. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() } fun handleResult(result: Result<String>): String { return when (result) { is Result.Success -> result.data is Result.Error -> result.exception.message } }
102. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() object Cancelled : Result<Nothing>() } fun handleResult(result: Result<String>): String { return when (result) { is Result.Success -> result.data is Result.Error -> result.exception.message } }
103. fun handleResult(result: Result<String>): String { return when (result) { is Result.Success -> result.data is Result.Error -> result.exception.message Result.Cancelled -> "cancelled" } } sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() object Cancelled : Result<Nothing>() }
104. sealed class Result<T> { data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() object Cancelled : Result<Nothing>() } fun handleResult(result: Result<String>): String { return when (result) { is Result.Success -> result.data is Result.Error -> result.exception.message Result.Cancelled -> "cancelled" } }
105. sealed class Result<T> data class Success<T>(val data: T) : Result<T>() data class Error(val exception: Exception) : Result<Nothing>() object Cancelled : Result<Nothing>() fun handleResult(result: Result<String>): String { return when (result) { is Success -> result.data is Error -> result.exception.message Cancelled -> "cancelled" } }
106. class Preferences(databaseName: String) { private val db = SqlDatabase(databaseName) fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?”) db.setTransactionSuccessful() } finally { db.endTransaction() } } }
107. class Preferences(databaseName: String) { private val db = SqlDatabase(databaseName) fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?”) db.setTransactionSuccessful() } finally { db.endTransaction() } } }
108. class Preferences(databaseName: String) { private val db by lazy { SqlDatabase(databaseName) } fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?”) db.setTransactionSuccessful() } finally { db.endTransaction() } } }
109. private val db by lazy { SqlDatabase(databaseName) }
110. private val db by lazy { SqlDatabase(databaseName) } var name by Delegates.observable("Drew") { prop, old, new !-> println("Name changed from $old to $new") }
111. private val db by lazy { SqlDatabase(databaseName) } var name by Delegates.observable("Drew") { prop, old, new !-> println("Name changed from $old to $new") } var address by Delegates.notNull<String>()
112. private val db by lazy { SqlDatabase(databaseName) } var name by Delegates.observable("Drew") { prop, old, new !-> println("Name changed from $old to $new") } var address by Delegates.notNull<String>() val labelView by bindView<TextView>(R.id.label)
113. class Preferences(databaseName: String) { private val db by lazy { SqlDatabase(databaseName) } fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?”) db.setTransactionSuccessful() } finally { db.endTransaction() } } } var name by Delegates.observable("Drew") { prop, old, new !-> println("Name changed from $old to $new") } var address by Delegates.notNull<String>() val labelView by bindView<TextView>(R.id.label)
114. class Preferences(databaseName: String) { private val db by lazy { SqlDatabase(databaseName) } fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?”) db.setTransactionSuccessful() } finally { db.endTransaction() } } } val labelView by bindView<TextView>(R.id.label)
115. fun delete(name: String) { db.beginTransaction() try { db.execute("DELETE FROM user WHERE name = ?") db.setTransactionSuccessful() } finally { db.endTransaction() } } class Preferences(databaseName: String) { private val db by lazy { SplDatabase(databaseName) } }
116. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
117. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
118. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
119. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
120. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
121. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { db.execute("DELETE FROM user WHERE name = ?") } }
122. fun SqlDatabase.transaction(func: () "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { db.execute("DELETE FROM user WHERE name = ?") } }
123. fun SqlDatabase.transaction(func: (SqlDatabase) "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { db.execute("DELETE FROM user WHERE name = ?") } } .execute("DELETE FROM user WHERE name = ?")
124. fun SqlDatabase.transaction(func: (SqlDatabase) "-> Unit) { beginTransaction() try { func(this) setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { db.execute("DELETE FROM user WHERE name = ?") } } .execute("DELETE FROM user WHERE name = ?")
125. fun SqlDatabase.transaction(func: (SqlDatabase) "-> Unit) { beginTransaction() try { func(this) setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { it.execute("DELETE FROM user WHERE name = ?") } } .execute("DELETE FROM user WHERE name = ?")
126. fun SqlDatabase.transaction(func: (SqlDatabase) "-> Unit) { beginTransaction() try { func(this) setTransactionSuccessful() } finally { endTransaction() } } fun delete(name: String) { db.transaction { it.execute("DELETE FROM user WHERE name = ?") } } .execute("DELETE FROM user WHERE name = ?")
127. fun delete(name: String) { db.transaction { it.execute("DELETE FROM user WHERE name = ?") } } fun SqlDatabase.transaction(func: SqlDatabase.() "-> Unit) { beginTransaction() try { func(this) setTransactionSuccessful() } finally { endTransaction() } }
128. fun delete(name: String) { db.transaction { it.execute("DELETE FROM user WHERE name = ?") } } fun SqlDatabase.transaction(func: SqlDatabase.() "-> Unit) { beginTransaction() try { this.func() setTransactionSuccessful() } finally { endTransaction() } }
129. fun delete(name: String) { db.transaction { it.execute("DELETE FROM user WHERE name = ?") } } fun SqlDatabase.transaction(func: SqlDatabase.() "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
130. fun delete(name: String) { db.transaction { execute("DELETE FROM user WHERE name = ?") } } fun SqlDatabase.transaction(func: SqlDatabase.() "-> Unit) { beginTransaction() try { func() setTransactionSuccessful() } finally { endTransaction() } }
131. data class User(val name: String, val age: Int)
132. @Serializable data class User(val name: String, val age: Int)
133. @Serializable data class User(val name: String, val age: Int) val drew = User("Drew", 5) val jsonString = Json.encodeToString(drew)
134. @Serializable data class User(val name: String, val age: Int) val drew = User("Drew", 5) val jsonString = Json.encodeToString(drew) println(jsonString) "// {"name":"Drew","age":5}
135. @Serializable data class User(val name: String, val age: Int) val drew = User("Drew", 5) val jsonString = Json.encodeToString(drew) println(jsonString) "// {"name":"Drew","age":5} val drew = Json.decodeFromString<User>(jsonString)
136. @Serializable data class User(val name: String, val age: Int) val drew = User("Drew", 5) val jsonString = Json.encodeToString(drew) println(jsonString) "// {"name":"Drew","age":5} val drew = Json.decodeFromString<User>(jsonString) println(drew) "// User(name=Drew, age=5)
137. @Serializable data class User(val name: String, val age: Int) val drew = User("Drew", 5) val jsonString = Json.encodeToString(drew) println(jsonString) "// {"name":"Drew","age":5} val drew = Json.decodeFromString<User>(jsonString) println(drew) "// User(name=Drew, age=5)
138. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
139. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
140. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
141. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
142. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
143. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
144. fun main() = runBlocking { repeat(100_000) { launch { delay(1.seconds) print(".") } } }
145. fun main() = runBlocking { repeat(100_000) { launch { delayAndPrint() } } } suspend fun delayAndPrint() { delay(1.seconds) print(".") }
146. fun main() = runBlocking { repeat(100_000) { launch { delayAndPrint() } } } suspend fun delayAndPrint() { delay(1.seconds) print(".") }
147. fun main() = runBlocking { repeat(100_000) { launch { delayAndPrint() } } } suspend fun delayAndPrint() { delay(1.seconds) print(".") }
148. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
149. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
150. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
151. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
152. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
153. suspend fun updateUserName() { Main { val user = Default { http.get("/api/user/1") } labelName.text = user.name } }
154. suspend fun updateUserName() { Main { val user = try { Default { http.get("/api/user/1") } } catch (e: HttpResponseException) { e.printStacktrace() null } labelName.text = user"?.name } }
155. suspend fun updateUserName() { Main { val user = try { Default { http.get("/api/user/1") } } catch (e: HttpResponseException) { e.printStacktrace() null } labelName.text = user"?.name } }