├── .gitignore
├── .idea
    ├── kotlinc.xml
    ├── libraries
    │   └── KotlinJavaRuntime.xml
    ├── misc.xml
    ├── modules.xml
    ├── uiDesigner.xml
    ├── vcs.xml
    └── workspace.xml
├── IdiomaticKotlin.iml
├── README.md
└── src
    ├── chap01_extension_functions
        ├── ExtensionFunction.kt
        ├── ExtensionProperties.kt
        └── InheritanceAndPolymorphism.kt
    ├── chap02_sealed_classes
        ├── LegacyApproach.kt
        └── SealedClass.kt
    ├── chap03_infix_function
        └── InfixFunction.kt
    ├── chap04_class_delegation
        └── DelegationSample.kt
    ├── chap05_local_function
        └── LocalFunction.kt
    ├── chap06_object_and_singleton
        └── Singleton.kt
    ├── chap07_sequence
        └── SequenceSample.kt
    ├── chap08_lambdas_sam_constructors
        ├── Invoke.kt
        ├── LambdaPass.kt
        ├── SAMConversion.kt
        └── View.java
    ├── chap09_lambda_receiver_dsl
        └── ViewCreator.kt
    ├── chap10_elvis_operator
        ├── ElvisSyntax.kt
        ├── ExpandedElvis.kt
        └── SafeCall.kt
    ├── chap11_property_delegation
        ├── Delegate.kt
        ├── LazyTest.kt
        ├── ManualLazy.kt
        └── ObservableTest.kt
    ├── chap12_higher_order_function_and_function_type
        └── FunctionType.kt
    ├── chap13_inline
        ├── InlinedFilter.kt
        ├── InlinedFunctionReference.kt
        ├── LambdaInstance.kt
        └── NotInlinedFilter.kt
    ├── chap14_lambda_and_control_flows
        ├── AnonymousFunctionReturns.kt
        ├── InlineReturn.kt
        ├── LambdaReturn.kt
        ├── NotinlineLambdaReturn.kt
        └── ReturnWithLabels.kt
    ├── chap15_reified_parameters
        ├── ReifiedParameter.kt
        ├── TypeErasure.kt
        └── TypeErasureLimitation.kt
    ├── chap16_noinline_crossinline
        ├── Crossinline.kt
        ├── Noinline.kt
        └── Safidfngd.java
    └── chap17_variance
        ├── Contravariance.java
        ├── Covariance.java
        ├── DeclarationSiteContravariance.kt
        ├── DeclarationSiteCovariance.kt
        ├── GenericInvariance.java
        ├── UseSiteVariance.kt
        └── Variance.java


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1 | out/
2 | 


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562 |           </folding>
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565 |     </entry>
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585 |       </provider>
586 |     </entry>
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598 |         </state>
599 |       </provider>
600 |     </entry>
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607 |     </entry>
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612 |         </state>
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619 |         </state>
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626 |         </state>
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629 |     <entry file="file://$PROJECT_DIR$/src/chap15_reified_parameters/TypeErasureLimitation.kt">
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640 |         </state>
641 |       </provider>
642 |     </entry>
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654 |         </state>
655 |       </provider>
656 |     </entry>
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658 |       <provider selected="true" editor-type-id="text-editor">
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661 |         </state>
662 |       </provider>
663 |     </entry>
664 |     <entry file="file://$PROJECT_DIR$/src/chap14_lambda_and_control_flows/AnonymousFunctionReturns.kt">
665 |       <provider selected="true" editor-type-id="text-editor">
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668 |         </state>
669 |       </provider>
670 |     </entry>
671 |     <entry file="file://$PROJECT_DIR$/src/chap16_noinline_crossinline/Safidfngd.java">
672 |       <provider selected="true" editor-type-id="text-editor">
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677 |             <element signature="e#584#585#0" expanded="true" />
678 |             <element signature="e#627#628#0" expanded="true" />
679 |           </folding>
680 |         </state>
681 |       </provider>
682 |     </entry>
683 |     <entry file="file://$PROJECT_DIR$/src/chap16_noinline_crossinline/Noinline.kt">
684 |       <provider selected="true" editor-type-id="text-editor">
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687 |         </state>
688 |       </provider>
689 |     </entry>
690 |     <entry file="jar://$KOTLIN_BUNDLED$/lib/kotlin-stdlib-sources.jar!/common/generated/_Collections.kt">
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694 |         </state>
695 |       </provider>
696 |     </entry>
697 |     <entry file="file://$PROJECT_DIR$/src/chap14_lambda_and_control_flows/NotinlineLambdaReturn.kt">
698 |       <provider selected="true" editor-type-id="text-editor">
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700 |           <caret line="10" lean-forward="true" selection-start-line="10" selection-end-line="10" />
701 |         </state>
702 |       </provider>
703 |     </entry>
704 |     <entry file="file://$PROJECT_DIR$/src/chap14_lambda_and_control_flows/InlineReturn.kt">
705 |       <provider selected="true" editor-type-id="text-editor">
706 |         <state relative-caret-position="442">
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708 |         </state>
709 |       </provider>
710 |     </entry>
711 |     <entry file="file://$PROJECT_DIR$/src/chap16_noinline_crossinline/Crossinline.kt">
712 |       <provider selected="true" editor-type-id="text-editor">
713 |         <state relative-caret-position="170">
714 |           <caret line="10" lean-forward="true" selection-start-line="10" selection-end-line="10" />
715 |         </state>
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717 |     </entry>
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722 |         </state>
723 |       </provider>
724 |     </entry>
725 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/Variance.java">
726 |       <provider selected="true" editor-type-id="text-editor">
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735 |         </state>
736 |       </provider>
737 |     </entry>
738 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/GenericInvariance.java">
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749 |         </state>
750 |       </provider>
751 |     </entry>
752 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/Contravariance.kt">
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756 |         </state>
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758 |     </entry>
759 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/Covariance.java">
760 |       <provider selected="true" editor-type-id="text-editor">
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768 |             <element signature="e#630#631#0" expanded="true" />
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770 |         </state>
771 |       </provider>
772 |     </entry>
773 |     <entry file="jar://C:/Program Files/Java/jdk-10/lib/src.zip!/java.base/java/util/List.java">
774 |       <provider selected="true" editor-type-id="text-editor">
775 |         <state relative-caret-position="355">
776 |           <caret line="571" column="6" selection-start-line="571" selection-start-column="6" selection-end-line="571" selection-end-column="6" />
777 |         </state>
778 |       </provider>
779 |     </entry>
780 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/DeclarationSiteCovariance.kt">
781 |       <provider selected="true" editor-type-id="text-editor">
782 |         <state relative-caret-position="187">
783 |           <caret line="11" lean-forward="true" selection-start-line="11" selection-end-line="11" />
784 |         </state>
785 |       </provider>
786 |     </entry>
787 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/DeclarationSiteContravariance.kt">
788 |       <provider selected="true" editor-type-id="text-editor">
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790 |           <caret line="13" lean-forward="true" selection-start-line="13" selection-end-line="13" />
791 |         </state>
792 |       </provider>
793 |     </entry>
794 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/Contravariance.java">
795 |       <provider selected="true" editor-type-id="text-editor">
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797 |           <caret line="37" selection-start-line="37" selection-end-line="37" />
798 |           <folding>
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800 |             <element signature="e#156#157#0" expanded="true" />
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802 |           </folding>
803 |         </state>
804 |       </provider>
805 |     </entry>
806 |     <entry file="file://$PROJECT_DIR$/src/chap17_variance/UseSiteVariance.kt">
807 |       <provider selected="true" editor-type-id="text-editor">
808 |         <state relative-caret-position="136">
809 |           <caret line="8" column="6" selection-start-line="8" selection-start-column="6" selection-end-line="8" selection-end-column="6" />
810 |         </state>
811 |       </provider>
812 |     </entry>
813 |   </component>
814 | </project>


--------------------------------------------------------------------------------
/IdiomaticKotlin.iml:
--------------------------------------------------------------------------------
 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <module type="JAVA_MODULE" version="4">
 3 |   <component name="NewModuleRootManager" inherit-compiler-output="true">
 4 |     <exclude-output />
 5 |     <content url="file://$MODULE_DIR$">
 6 |       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
 7 |     </content>
 8 |     <orderEntry type="inheritedJdk" />
 9 |     <orderEntry type="sourceFolder" forTests="false" />
10 |     <orderEntry type="library" name="KotlinJavaRuntime" level="project" />
11 |   </component>
12 | </module>


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
 1 | # Idiomatic Kotlin
 2 | Contains all the code presented in the Idiomatic Kotlin tutorial series.
 3 | 
 4 | ## Chapters:
 5 | 1. [Idiomatic Kotlin: Extension functions](https://medium.com/tompee/idiomatic-kotlin-extension-functions-67735491851f)
 6 | 2. [Idiomatic Kotlin: Sealed Classes](https://medium.com/tompee/idiomatic-kotlin-sealed-classes-bf1772d9d607)
 7 | 3. [Idiomatic Kotlin: Infix functions](https://medium.com/tompee/idiomatic-kotlin-infix-functions-eea833f70c90)
 8 | 4. [Idiomatic Kotlin: Class Delegates](https://medium.com/tompee/idiomatic-kotlin-class-delegates-288b24c37ac8)
 9 | 5. [Idiomatic Kotlin: Local functions](https://medium.com/tompee/idiomatic-kotlin-local-functions-4421f86ac864)
10 | 6. [Idiomatic Kotlin: Object and Singleton](https://medium.com/tompee/idiomatic-kotlin-object-and-singleton-183c3cfdbd26)
11 | 7. [Idiomatic Kotlin: Sequences](https://medium.com/tompee/idiomatic-kotlin-sequences-80ebbeec1115)
12 | 8. [Idiomatic Kotlin: Lambdas and SAM constructors](https://medium.com/tompee/idiomatic-kotlin-lambdas-and-sam-constructors-fe2075965bfb)
13 | 9. [Idiomatic Kotlin: Lambdas with Receiver and DSL](https://medium.com/tompee/idiomatic-kotlin-lambdas-with-receiver-and-dsl-3cd3348e1235)
14 | 10. [Idiomatic Kotlin: Elvis Operator](https://medium.com/tompee/idiomatic-kotlin-elvis-operator-d6f5639a5130)
15 | 11. [Idiomatic Kotlin: Property Delegates and Lazy](https://medium.com/tompee/idiomatic-kotlin-property-delegates-and-lazy-11207213a788)
16 | 12. [Idiomatic Kotlin: Higher-order functions and Function Types](https://medium.com/tompee/idiomatic-kotlin-higher-order-functions-and-function-types-adb59172796)
17 | 13. [Idiomatic Kotlin: Inline functions](https://medium.com/tompee/idiomatic-kotlin-inline-functions-e39b2f90a291)
18 | 14. [Idiomatic Kotlin: Lambdas and Control Flows](https://medium.com/tompee/idiomatic-kotlin-lambdas-and-control-flows-70a7a58d7a20)
19 | 15. [Idiomatic Kotlin: Reified Parameters](https://medium.com/tompee/idiomatic-kotlin-reified-parameters-e89f665ab026)
20 | 16. [Idiomatic Kotlin: Noinline and Crossinline](https://medium.com/tompee/idiomatic-kotlin-noinline-and-crossinline-e51014408ff0)
21 | 17. [Idiomatic Kotlin: Variance](https://medium.com/tompee/idiomatic-kotlin-variance-82355d9a71df)
22 | 18. [Idiomatic Kotlin: Annotations and Reflection](https://medium.com/tompee/kotlin-annotations-and-reflection-caa0d73bf39b)
23 | 19. [Idiomatic Kotlin: Annotation Processor and Code Generation](https://medium.com/tompee/kotlin-annotation-processor-and-code-generation-58bd7d0d333b)
24 | 
25 | Check out all the other articles on the publication as well [here](https://medium.com/tompee).
26 | 


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/src/chap01_extension_functions/ExtensionFunction.kt:
--------------------------------------------------------------------------------
1 | package chap01_extension_functions
2 | 
3 | class ExtensionFunction {
4 |     fun String.second(): Char {
5 |         if (isEmpty()) throw NoSuchElementException("Char sequence is empty.")
6 |         if (length < 2) throw NoSuchElementException("Char sequence length is less than 2.")
7 |         return this[1]
8 |     }
9 | }


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/src/chap01_extension_functions/ExtensionProperties.kt:
--------------------------------------------------------------------------------
 1 | package chap01_extension_functions
 2 | 
 3 | class ExtensionProperties {
 4 |     val String.second: Char
 5 |         get() {
 6 |             if (isEmpty()) throw NoSuchElementException("Char sequence is empty.")
 7 |             if (length < 2) throw NoSuchElementException("Char sequence length is less than 2.")
 8 |             return this[1]
 9 |         }
10 | }


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/src/chap01_extension_functions/InheritanceAndPolymorphism.kt:
--------------------------------------------------------------------------------
 1 | package chap01_extension_functions
 2 | 
 3 | class InheritanceAndPolymorphism {
 4 |     open class Base {
 5 |         open fun getString() = "Base"
 6 |     }
 7 | 
 8 |     fun Base.newString() = "BaseNewString"
 9 | 
10 |     class Derived : Base() {
11 |         override fun getString() = "Derived"
12 |     }
13 | 
14 |     fun Derived.newString() = "DerivedNewString"
15 | }
16 | 


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/src/chap02_sealed_classes/LegacyApproach.kt:
--------------------------------------------------------------------------------
 1 | package chap02_sealed_classes
 2 | 
 3 | class LegacyApproach {
 4 |     interface Class
 5 | 
 6 |     class Knight : Class
 7 | 
 8 |     class Priest : Class
 9 | 
10 |     fun getClassString(clazz: Class): String {
11 |         return when (clazz) {
12 |             is Knight -> "Knight"
13 |             is Priest -> "Priest"
14 |             else -> throw IllegalArgumentException("Unknown class")
15 |         }
16 |     }
17 | }
18 | 


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/src/chap02_sealed_classes/SealedClass.kt:
--------------------------------------------------------------------------------
 1 | package chap02_sealed_classes
 2 | 
 3 | sealed class Attribute
 4 | 
 5 | class Intelligence : Attribute()
 6 | 
 7 | class Agility : Attribute()
 8 | 
 9 | class Strength : Attribute()
10 | 
11 | fun getAttributeString(attribute: Attribute): String {
12 |     return when (attribute) {
13 |         is Intelligence -> "Intelligence"
14 |         is Strength -> "Strength"
15 |         is Agility -> "Agility"
16 |     }
17 | }
18 | 


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/src/chap03_infix_function/InfixFunction.kt:
--------------------------------------------------------------------------------
 1 | package chap03_infix_function
 2 | 
 3 | class InfixFunction {
 4 |     class Warrior(var hp: Int, var ap: Int) {
 5 |         infix fun attack(anotherWarrior: Warrior) {
 6 |             anotherWarrior.hp -= ap
 7 |         }
 8 |     }
 9 | 
10 |     fun attackTest() {
11 |         val warrior1 = Warrior(100, 20)
12 |         val warrior2 = Warrior(100, 15)
13 | 
14 |         warrior1 attack warrior2
15 |         println("Warrior 2 HP : ${warrior2.hp}")
16 |     }
17 | }


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/src/chap04_class_delegation/DelegationSample.kt:
--------------------------------------------------------------------------------
 1 | package chap04_class_delegation
 2 | 
 3 | class DelegationSample {
 4 |     interface AttackType {
 5 |         fun getAttackType(): String
 6 |     }
 7 | 
 8 |     class Ranged : AttackType {
 9 |         override fun getAttackType(): String = "Ranged"
10 |     }
11 | 
12 |     interface HeroType {
13 |         fun getAttributeType(): String
14 |     }
15 | 
16 |     class Strength : HeroType {
17 |         override fun getAttributeType(): String = "Strength"
18 |     }
19 | 
20 |     class Huskar : AttackType by Ranged(), HeroType by Strength()
21 | }


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/src/chap05_local_function/LocalFunction.kt:
--------------------------------------------------------------------------------
 1 | package chap05_local_function
 2 | 
 3 | class LocalFunction {
 4 |     // Local function
 5 |     fun login(username: String, password: String): Boolean {
 6 |         var something = 1
 7 |         fun validateInput(input: String) {
 8 |             something++
 9 |             if (input.isEmpty()) {
10 |                 throw IllegalArgumentException("Must not be empty")
11 |             }
12 |         }
13 |         validateInput(username)
14 |         validateInput(password)
15 |         return true
16 |     }
17 | 
18 |     data class Credentials(val username: String, val password: String)
19 | 
20 |     // Local extension function
21 |     fun Credentials.validate() {
22 |         fun validateInput(input: String) {
23 |             if (input.isEmpty()) {
24 |                 throw IllegalArgumentException("Must not be empty")
25 |             }
26 |         }
27 |         validateInput(username)
28 |         validateInput(password)
29 |     }
30 | 
31 |     fun login(credentials: Credentials) {
32 |         credentials.validate()
33 |     }
34 | }


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/src/chap06_object_and_singleton/Singleton.kt:
--------------------------------------------------------------------------------
 1 | package chap06_object_and_singleton
 2 | 
 3 | import java.io.Serializable
 4 | 
 5 | object Singleton : Serializable {
 6 |     val text: String = "Hello from singleton"
 7 | 
 8 |     init {
 9 |         /* Do initialization here */
10 |     }
11 | }


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/src/chap07_sequence/SequenceSample.kt:
--------------------------------------------------------------------------------
 1 | package chap07_sequence
 2 | 
 3 | // Copy of some stdlib functions. Use the actual function in stdlib for the latest code
 4 | class SequenceSample {
 5 |     public inline fun <T> Iterable<T>.filter(predicate: (T) -> Boolean): List<T> {
 6 |         return filterTo(ArrayList<T>(), predicate)
 7 |     }
 8 | 
 9 |     public inline fun <T, C : MutableCollection<in T>> Iterable<T>.filterTo(destination: C, predicate: (T) -> Boolean): C {
10 |         for (element in this) if (predicate(element)) destination.add(element)
11 |         return destination
12 |     }
13 | 
14 |     public fun <T> Sequence<T>.filter(predicate: (T) -> Boolean): Sequence<T> {
15 |         return FilteringSequence(this, true, predicate)
16 |     }
17 | 
18 |     internal class FilteringSequence<T>(
19 |             private val sequence: Sequence<T>,
20 |             private val sendWhen: Boolean = true,
21 |             private val predicate: (T) -> Boolean
22 |     ) : Sequence<T> {
23 | 
24 |         override fun iterator(): Iterator<T> = object : Iterator<T> {
25 |             val iterator = sequence.iterator()
26 |             var nextState: Int = -1 // -1 for unknown, 0 for done, 1 for continue
27 |             var nextItem: T? = null
28 | 
29 |             private fun calcNext() {
30 |                 while (iterator.hasNext()) {
31 |                     val item = iterator.next()
32 |                     if (predicate(item) == sendWhen) {
33 |                         nextItem = item
34 |                         nextState = 1
35 |                         return
36 |                     }
37 |                 }
38 |                 nextState = 0
39 |             }
40 | 
41 |             override fun next(): T {
42 |                 if (nextState == -1)
43 |                     calcNext()
44 |                 if (nextState == 0)
45 |                     throw NoSuchElementException()
46 |                 val result = nextItem
47 |                 nextItem = null
48 |                 nextState = -1
49 |                 @Suppress("UNCHECKED_CAST")
50 |                 return result as T
51 |             }
52 | 
53 |             override fun hasNext(): Boolean {
54 |                 if (nextState == -1)
55 |                     calcNext()
56 |                 return nextState == 1
57 |             }
58 |         }
59 |     }
60 | }


--------------------------------------------------------------------------------
/src/chap08_lambdas_sam_constructors/Invoke.kt:
--------------------------------------------------------------------------------
 1 | package chap08_lambdas_sam_constructors
 2 | 
 3 | fun main(args: Array<String>) {
 4 |     // Regular f(x)
 5 |     val addOffset = { x: Int -> x + 1 }
 6 |     println(addOffset(2))
 7 | 
 8 |     // Invoke
 9 |     println(addOffset.invoke(2))
10 | 
11 |     // Anonymous invocation
12 |     println({ x: Int -> x + 1 }(2))
13 | }
14 | 


--------------------------------------------------------------------------------
/src/chap08_lambdas_sam_constructors/LambdaPass.kt:
--------------------------------------------------------------------------------
 1 | package chap08_lambdas_sam_constructors
 2 | 
 3 | fun main(args: Array<String>) {
 4 |     fun addOffset(base: Int, lambda: (Int) -> Int): Int {
 5 |         return lambda.invoke(base)
 6 |     }
 7 | 
 8 |     fun addOffset(lambda: (Int) -> Int, base: Int): Int {
 9 |         return lambda.invoke(2)
10 |     }
11 | 
12 |     // Last argument lambda
13 |     addOffset(2) { x: Int -> x + 1 }
14 | 
15 |     // General syntax
16 |     addOffset({ x: Int -> x + 1 }, 2)
17 | }


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/src/chap08_lambdas_sam_constructors/SAMConversion.kt:
--------------------------------------------------------------------------------
 1 | package chap08_lambdas_sam_constructors
 2 | 
 3 | fun main(args: Array<String>) {
 4 |     // Assigning to a variable
 5 |     val runnable: Runnable = Runnable { print("I am a runnable") }
 6 | 
 7 |     // Returning a specific type of functional interface
 8 |     fun createOnClickListener(): View.OnClickListener {
 9 |         return View.OnClickListener { v -> print("I am clicked") }
10 |     }
11 | }


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/src/chap08_lambdas_sam_constructors/View.java:
--------------------------------------------------------------------------------
1 | package chap08_lambdas_sam_constructors;
2 | 
3 | public class View {
4 |     interface OnClickListener {
5 |         void onClick(View view);
6 |     }
7 | }
8 | 


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/src/chap09_lambda_receiver_dsl/ViewCreator.kt:
--------------------------------------------------------------------------------
 1 | package chap09_lambda_receiver_dsl
 2 | 
 3 | class ViewCreator {
 4 |     class XMLChildContainer : XMLContainer() {
 5 |         private val tagData = StringBuilder()
 6 | 
 7 |         fun attr(attrName: String, value: String) {
 8 |             tagData.append(" $attrName=\"$value\"")
 9 |         }
10 | 
11 |         fun attrData() = tagData.toString()
12 |     }
13 | 
14 |     open class XMLContainer {
15 |         private val data = StringBuilder()
16 | 
17 |         fun child(tag: String, action: XMLChildContainer.() -> Unit): XMLContainer {
18 |             data.append("<$tag")
19 |             val tagData = XMLChildContainer()
20 |             tagData.action()
21 |             data.append(tagData.attrData())
22 |             data.append(">")
23 |             data.append(tagData.data())
24 |             data.append("\n</$tag>")
25 |             return this
26 |         }
27 | 
28 |         fun data() = data.toString()
29 |     }
30 | }
31 | 
32 | fun createAndroidLayout(): ViewCreator.XMLContainer {
33 |     return ViewCreator.XMLContainer()
34 | }
35 | 
36 | fun main(args: Array<String>) {
37 |     val xml = createAndroidLayout()
38 |             .child("LinearLayout") {
39 |                 attr("android:layout_height", "match_parent")
40 |                 attr("android:layout_width", "match_parent")
41 |                 attr("android:orientation", "vertical")
42 |                 child("ImageView") {
43 |                     attr("android:layout_height", "match_parent")
44 |                     attr("android:layout_width", "match_parent")
45 |                 }
46 |                 child("TextView") {
47 |                     attr("android:layout_height", "match_parent")
48 |                     attr("android:layout_width", "match_parent")
49 |                 }
50 |             }
51 |     println(xml.data())
52 | }


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/src/chap10_elvis_operator/ElvisSyntax.kt:
--------------------------------------------------------------------------------
1 | package chap10_elvis_operator
2 | 
3 | class ElvisSyntax {
4 |     fun elvisSample(arg: String?) {
5 |         val value = arg ?: ""
6 |     }
7 | }


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/src/chap10_elvis_operator/ExpandedElvis.kt:
--------------------------------------------------------------------------------
1 | package chap10_elvis_operator
2 | 
3 | class ExpandedElvis {
4 |     fun elvisSample(arg: String?) {
5 |         val value = if (arg != null) arg else ""
6 |     }
7 | }


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/src/chap10_elvis_operator/SafeCall.kt:
--------------------------------------------------------------------------------
 1 | package chap10_elvis_operator
 2 | 
 3 | class SafeCall {
 4 |     data class Person(val name: String, val age: Int)
 5 | 
 6 |     fun safeCallTest() {
 7 |         val john: Person? = Person("John", 32)
 8 | 
 9 |         val age = john?.age
10 |         // Uncomment to experience compile error
11 |         //val offsetAge = age + 1 /* compile error */
12 |     }
13 | 
14 |     fun elvisDefault() {
15 |         val john: Person? = Person("John", 32)
16 | 
17 |         val age = john?.age ?: 25
18 |         val offsetAge = age + 1 /* no compile error */
19 |     }
20 | 
21 |     fun elvisThrow() {
22 |         val john : Person? = Person("John", 32)
23 | 
24 |         val age = john?.age ?: throw IllegalArgumentException("John is null")
25 |         val offsetAge = age + 1 /* no compile error */
26 |     }
27 | }


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/src/chap11_property_delegation/Delegate.kt:
--------------------------------------------------------------------------------
 1 | package chap11_property_delegation
 2 | 
 3 | import kotlin.properties.ReadOnlyProperty
 4 | import kotlin.reflect.KProperty
 5 | 
 6 | class DelegateTest {
 7 |     val name: String by NameDelegate(Database())
 8 | }
 9 | 
10 | class Database {
11 |     fun queryName(): String = "Sample results"
12 | }
13 | 
14 | class NameDelegate<T>(private val db: Database) : ReadOnlyProperty<T, String> {
15 |     override fun getValue(thisRef: T, property: KProperty<*>): String = db.queryName()
16 | }


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/src/chap11_property_delegation/LazyTest.kt:
--------------------------------------------------------------------------------
1 | package chap11_property_delegation
2 | 
3 | class LazyTest {
4 |     data class Hero(val attribute: String, val attackType: String)
5 | 
6 |     val _hero: Hero by lazy { Hero("agility", "melee") }
7 | }


--------------------------------------------------------------------------------
/src/chap11_property_delegation/ManualLazy.kt:
--------------------------------------------------------------------------------
 1 | package chap11_property_delegation
 2 | 
 3 | class ManualLazy {
 4 |     data class Hero(val attribute: String, val attackType: String)
 5 | 
 6 |     private var _hero: Hero? = null
 7 | 
 8 |     val hero: Hero
 9 |         get() {
10 |             if (_hero == null) {
11 |                 _hero = Hero("agility", "melee")
12 |             }
13 |             return _hero!!
14 |         }
15 | }


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/src/chap11_property_delegation/ObservableTest.kt:
--------------------------------------------------------------------------------
 1 | package chap11_property_delegation
 2 | 
 3 | import kotlin.properties.Delegates
 4 | 
 5 | class ObservableTest {
 6 |     data class Hero(val attribute: String, val attackType: String)
 7 | 
 8 |     var hero: Hero by Delegates.observable(Hero("agility", "melee")) { prop, old, new ->
 9 |         /* Do something here */
10 |     }
11 | }


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/src/chap12_higher_order_function_and_function_type/FunctionType.kt:
--------------------------------------------------------------------------------
1 | package chap12_higher_order_function_and_function_type
2 | 
3 | 
4 | // A copy of stdlib function interface. Please check actual stdlib function for the updated code
5 | /** A function that takes 1 argument. */
6 | public interface Function1<in P1, out R> : Function<R> {
7 |     /** Invokes the function with the specified argument. */
8 |     public operator fun invoke(p1: P1): R
9 | }


--------------------------------------------------------------------------------
/src/chap13_inline/InlinedFilter.kt:
--------------------------------------------------------------------------------
 1 | package chap13_inline
 2 | 
 3 | class InlinedFilter {
 4 |     inline fun inlinedFilter(list: List<Int>, predicate: (Int) -> Boolean): List<Int> {
 5 |         return list.filter(predicate)
 6 |     }
 7 | 
 8 |     fun lambdaInCallSiteTest() {
 9 |         val list = listOf(1, 2, 3)
10 |         val newList = inlinedFilter(list) { it < 2 }
11 |         println(newList)
12 |     }
13 | }


--------------------------------------------------------------------------------
/src/chap13_inline/InlinedFunctionReference.kt:
--------------------------------------------------------------------------------
 1 | package chap13_inline
 2 | 
 3 | class InlinedFunctionReference {
 4 |     inline fun inlinedFilter(list: List<Int>, predicate: (Int) -> Boolean): List<Int> {
 5 |         return list.filter(predicate)
 6 |     }
 7 | 
 8 |     fun filterLessThanTwo(input: Int) = input < 2
 9 | 
10 |     fun functionReferenceTest() {
11 |         val list = listOf(1, 2, 3)
12 |         val newList = inlinedFilter(list, ::filterLessThanTwo)
13 |         println(newList)
14 |     }
15 | }


--------------------------------------------------------------------------------
/src/chap13_inline/LambdaInstance.kt:
--------------------------------------------------------------------------------
 1 | package chap13_inline
 2 | 
 3 | class LambdaInstance {
 4 |     inline fun inlinedFilter(list: List<Int>, predicate: (Int) -> Boolean): List<Int> {
 5 |         return list.filter(predicate)
 6 |     }
 7 | 
 8 |     fun filterLessThanTwo(input: Int) = input < 2
 9 | 
10 |     fun lambdaInstance(predicate: (Int) -> Boolean) {
11 |         val list = listOf(1, 2, 3)
12 |         val newList = inlinedFilter(list, predicate)
13 |         println(newList)
14 |     }
15 | 
16 |     fun lambdaInstanceTest() {
17 |         lambdaInstance(::filterLessThanTwo)
18 |     }
19 | }


--------------------------------------------------------------------------------
/src/chap13_inline/NotInlinedFilter.kt:
--------------------------------------------------------------------------------
 1 | package chap13_inline
 2 | 
 3 | class NotInlinedFilter {
 4 |     fun notInlinedFilter(list: List<Int>, predicate: (Int) -> Boolean): List<Int> {
 5 |         return list.filter(predicate)
 6 |     }
 7 | 
 8 |     fun notInlinedTest() {
 9 |         val list = listOf(1, 2, 3)
10 |         val newList = notInlinedFilter(list) { it < 2 }
11 |         println(newList)
12 |     }
13 | }


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/src/chap14_lambda_and_control_flows/AnonymousFunctionReturns.kt:
--------------------------------------------------------------------------------
 1 | package chap14_lambda_and_control_flows
 2 | 
 3 | class AnonymousFunctionReturns {
 4 |     data class Student(val name: String, val id: Int)
 5 | 
 6 |     private fun findSpock(list: List<Student>) {
 7 |         list.forEach(fun(student) {
 8 |             if (student.name == "Spock") {
 9 |                 println("Found Spock")
10 |                 return
11 |             }
12 |         })
13 |         println("Did we find Spock?")
14 |     }
15 | 
16 |     fun findStudentTest() {
17 |         val studentList = listOf(Student("Kirk", 12345), Student("Spock", 54321))
18 |         findSpock(studentList)
19 |         println("End of findStudentTest")
20 |     }
21 | }
22 | 
23 | fun main(args: Array<String>) {
24 |     val test = AnonymousFunctionReturns()
25 |     test.findStudentTest()
26 | }


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/src/chap14_lambda_and_control_flows/InlineReturn.kt:
--------------------------------------------------------------------------------
 1 | package chap14_lambda_and_control_flows
 2 | 
 3 | class InlineReturn {
 4 |     data class Student(val name: String, val id: Int)
 5 | 
 6 |     private inline fun findSpock(list: List<Student>, func: (Student) -> Unit) {
 7 |         list.forEach { func(it) }
 8 |         println("Did we find Spock?")
 9 |     }
10 | 
11 |     fun findStudentTest() {
12 |         val studentList = listOf(Student("Kirk", 12345), Student("Spock", 54321))
13 |         findSpock(studentList) {
14 |             if (it.name == "Spock") {
15 |                 println("Found Spock")
16 |                 return
17 |             }
18 |             println("Not Spock")
19 |         }
20 |         println("End of findStudentTest")
21 |     }
22 | }
23 | 
24 | fun main(args: Array<String>) {
25 |     val test = InlineReturn()
26 |     test.findStudentTest()
27 | }


--------------------------------------------------------------------------------
/src/chap14_lambda_and_control_flows/LambdaReturn.kt:
--------------------------------------------------------------------------------
 1 | package chap14_lambda_and_control_flows
 2 | 
 3 | class LambdaReturn {
 4 |     data class Student(val name: String, val id: Int)
 5 | 
 6 |     private fun findSpock(list: List<Student>) {
 7 |         list.forEach {
 8 |             if (it.name == "Spock") {
 9 |                 println("Found Spock")
10 |                 return
11 |             }
12 |         }
13 |         println("Spock not found")
14 |     }
15 | 
16 |     fun findStudentTest() {
17 |         val studentList = listOf(Student("Kirk", 12345), Student("Spock", 54321))
18 |         findSpock(studentList)
19 |         println("End of findStudentTest")
20 |     }
21 | }
22 | 
23 | fun main(args: Array<String>) {
24 |     val test = LambdaReturn()
25 |     test.findStudentTest()
26 | }


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/src/chap14_lambda_and_control_flows/NotinlineLambdaReturn.kt:
--------------------------------------------------------------------------------
 1 | package chap14_lambda_and_control_flows
 2 | 
 3 | fun higherOrderFunction(lambda : () -> Unit) {
 4 | }
 5 | 
 6 | fun lambdaReturnTest() {
 7 |     higherOrderFunction(fun() {
 8 |         return
 9 |     })
10 | }
11 | 


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/src/chap14_lambda_and_control_flows/ReturnWithLabels.kt:
--------------------------------------------------------------------------------
 1 | package chap14_lambda_and_control_flows
 2 | 
 3 | class ReturnWithLabels {
 4 |     data class Student(val name: String, val id: Int)
 5 | 
 6 |     private fun findSpock(list: List<Student>) {
 7 |         list.forEach label@{
 8 |             // or simply omit and use return@foreach instead
 9 |             if (it.name == "Spock") {
10 |                 println("Found Spock")
11 |                 return@label
12 |             }
13 |         }
14 |         println("Did we find Spock?")
15 |     }
16 | 
17 |     fun findStudentTest() {
18 |         val studentList = listOf(Student("Kirk", 12345), Student("Spock", 54321))
19 |         findSpock(studentList)
20 |         println("End of findStudentTest")
21 |     }
22 | }
23 | 
24 | fun main(args: Array<String>) {
25 |     val test = ReturnWithLabels()
26 |     test.findStudentTest()
27 | }


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/src/chap15_reified_parameters/ReifiedParameter.kt:
--------------------------------------------------------------------------------
 1 | package chap15_reified_parameters
 2 | 
 3 | inline fun <reified T> doSomethingWithType(obj: T) {
 4 |     val typeName = T::class.java
 5 |     println(typeName)
 6 | }
 7 | 
 8 | fun main(args: Array<String>) {
 9 |     doSomethingWithType(String())
10 | }


--------------------------------------------------------------------------------
/src/chap15_reified_parameters/TypeErasure.kt:
--------------------------------------------------------------------------------
1 | package chap15_reified_parameters
2 | 
3 | fun <T> getCount(list : List<T>) : Int = list.size


--------------------------------------------------------------------------------
/src/chap15_reified_parameters/TypeErasureLimitation.kt:
--------------------------------------------------------------------------------
 1 | package chap15_reified_parameters
 2 | 
 3 | fun <T> isListOfString(arg: T): Boolean {
 4 |     // Uncomment to experience compile error
 5 |     //return arg is List<String> // Compile error
 6 |     return true
 7 | }
 8 | 
 9 | fun <T> isList(arg: T): Boolean {
10 |     return arg is List<*>
11 | }


--------------------------------------------------------------------------------
/src/chap16_noinline_crossinline/Crossinline.kt:
--------------------------------------------------------------------------------
 1 | package chap16_noinline_crossinline
 2 | 
 3 | fun someHigherOrderFunction(message: String, func: (String) -> Unit) {
 4 | }
 5 | 
 6 | inline fun crossInlineTest(message: String, crossinline func: (String) -> Unit) {
 7 |     someHigherOrderFunction("crossInlineTest") {
 8 |         func(it) // Compile error here
 9 |     }
10 | }
11 | 
12 | fun main(arg: Array<String>) {
13 |     someHigherOrderFunction("Hello") {
14 |         println(it)
15 |         // Uncomment to experience compile error
16 |         //return // Compile error here because crossinline does not allow return
17 |     }
18 |     println("Main finished")
19 | }
20 | 


--------------------------------------------------------------------------------
/src/chap16_noinline_crossinline/Noinline.kt:
--------------------------------------------------------------------------------
1 | package chap16_noinline_crossinline
2 | 
3 | inline fun <reified T> doSomething(obj: T, noinline func: (T) -> T) {
4 |     func(obj)
5 | }
6 | 
7 | fun main(args: Array<String>) {
8 |     doSomething(String()) { it }
9 | }


--------------------------------------------------------------------------------
/src/chap16_noinline_crossinline/Safidfngd.java:
--------------------------------------------------------------------------------
 1 | package chap16_noinline_crossinline;
 2 | 
 3 | import kotlin.jvm.functions.Function1;
 4 | import kotlin.jvm.internal.Intrinsics;
 5 | import org.jetbrains.annotations.NotNull;
 6 | 
 7 | public class Safidfngd {
 8 |     private static final void doSomething(Object obj, Function1 func) {
 9 |         func.invoke(obj);
10 |     }
11 | 
12 |     public static final void main(@NotNull String[] args) {
13 |         Intrinsics.checkParameterIsNotNull(args, "args");
14 |         String obj$iv = new String();
15 |         Function1 func$iv = (Function1) new Function1<String, String>() {
16 |             @Override
17 |             public String invoke(String s) {
18 |                 return s;
19 |             }
20 |         };
21 |         func$iv.invoke(obj$iv);
22 |     }
23 | }
24 | 


--------------------------------------------------------------------------------
/src/chap17_variance/Contravariance.java:
--------------------------------------------------------------------------------
 1 | package chap17_variance;
 2 | 
 3 | import java.util.ArrayList;
 4 | import java.util.List;
 5 | 
 6 | public class Contravariance {
 7 |     public static void main(String... args) {
 8 |         varianceTest();
 9 |     }
10 | 
11 |     public static void varianceTest() {
12 |         List<Number> numbers = new ArrayList<>();
13 |         genericVariance(numbers);
14 | 
15 |         List<Object> objects = new ArrayList<>();
16 |         genericVariance(objects);
17 |     }
18 | 
19 | 
20 |     public static void genericVariance(List<? super Number> numbers) {
21 |         numbers.add(new Double(12));
22 |         numbers.add(new Float(12));
23 |     }
24 | 
25 |     public static void contravarianceProblem() {
26 |         List<? super Number> numberList = getNumberList();
27 |         numberList.add(new Long(12));
28 |         numberList.add(new Double(12));
29 | 
30 |         //Number number = numberList.get(0); // compile error
31 |     }
32 | 
33 |     public static List<? super Number> getNumberList() {
34 |         List<Object> objects = new ArrayList<>();
35 |         objects.add("");
36 |         return objects;
37 |     }
38 | }
39 | 


--------------------------------------------------------------------------------
/src/chap17_variance/Covariance.java:
--------------------------------------------------------------------------------
 1 | package chap17_variance;
 2 | 
 3 | import java.util.ArrayList;
 4 | import java.util.List;
 5 | 
 6 | public class Covariance {
 7 |     public static void main(String... args) {
 8 |         varianceTest();
 9 |     }
10 | 
11 |     public static void varianceTest() {
12 |         List<Number> numbers = new ArrayList<>();
13 |         genericVariance(numbers);
14 | 
15 |         List<Integer> integers = new ArrayList<>();
16 |         genericVariance(integers);
17 |     }
18 | 
19 | 
20 |     public static void genericVariance(List<? extends Number> numbers) {
21 |     }
22 | 
23 |     public static void covarianceProblem() {
24 |         //getNumberList().add(new Long(12)); // Compile error
25 |     }
26 | 
27 |     public static List<? extends Number> getNumberList() {
28 |         return new ArrayList<Integer>();
29 |     }
30 | }
31 | 


--------------------------------------------------------------------------------
/src/chap17_variance/DeclarationSiteContravariance.kt:
--------------------------------------------------------------------------------
 1 | package chap17_variance
 2 | 
 3 | interface Consumer<in T> {
 4 |     fun consume(input: T): Boolean
 5 | }
 6 | 
 7 | class NumberConsumer : Consumer<Number> {
 8 |     override fun consume(input: Number): Boolean = true
 9 | }
10 | 
11 | fun checkConsumer(consumer: NumberConsumer) {
12 |     val anyConsumer: Consumer<Int> = consumer
13 | }
14 | 
15 | 


--------------------------------------------------------------------------------
/src/chap17_variance/DeclarationSiteCovariance.kt:
--------------------------------------------------------------------------------
 1 | package chap17_variance
 2 | 
 3 | interface Producer<out T> {
 4 |     fun produce(): T
 5 | }
 6 | 
 7 | class NumberProducer : Producer<Number> {
 8 |     override fun produce(): Number = Math.random()
 9 | }
10 | 
11 | val producer: Producer<Any> = NumberProducer()
12 | 


--------------------------------------------------------------------------------
/src/chap17_variance/GenericInvariance.java:
--------------------------------------------------------------------------------
 1 | package chap17_variance;
 2 | 
 3 | import java.util.ArrayList;
 4 | import java.util.List;
 5 | 
 6 | public class GenericInvariance {
 7 |     public static void main (String... args) {
 8 |         varianceTest();
 9 |     }
10 | 
11 |     public static void varianceTest() {
12 |         List<Number> numbers = new ArrayList<>();
13 |         genericVariance(numbers);
14 | 
15 |         List<Integer> integers = new ArrayList<>();
16 |         //genericVariance(integers); // compile error
17 |     }
18 | 
19 |     public static void genericVariance(List<Number> numbers) {
20 |         numbers.add(new Long(12));
21 |     }
22 | }
23 | 


--------------------------------------------------------------------------------
/src/chap17_variance/UseSiteVariance.kt:
--------------------------------------------------------------------------------
 1 | package chap17_variance
 2 | 
 3 | interface Group<T> {
 4 |     fun setGroup(value: T)
 5 |     fun getGroup(): T
 6 | }
 7 | 
 8 | fun doSomething(input1: Group<out Number>, input2: Group<in Number>) {
 9 |     //input1.setGroup(12) // compile error
10 |     val outGroup: Number = input1.getGroup()
11 | 
12 |     input2.setGroup(12)
13 |     //val inGroup: Number = input2.getGroup() // compile error
14 | }


--------------------------------------------------------------------------------
/src/chap17_variance/Variance.java:
--------------------------------------------------------------------------------
 1 | package chap17_variance;
 2 | 
 3 | public class Variance {
 4 | 
 5 |     public static void main (String... args) {
 6 |         varianceTest();
 7 |     }
 8 | 
 9 |     public static void varianceTest() {
10 |         Number[] numbers = new Number[12];
11 |         arrayVariance(numbers);
12 | 
13 |         Integer[] integers = new Integer[12];
14 |         arrayVariance(integers);
15 |     }
16 | 
17 |     public static void arrayVariance(Number[] numbers) {
18 |         numbers[0] = new Long(12);
19 |     }
20 | }
21 | 


--------------------------------------------------------------------------------