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Add subheading about finality of classes

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Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>
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Harsh Shandilya 2019-09-21 23:42:17 +05:30
parent 2f67fe19a5
commit 476fd2935b
1 changed files with 5 additions and 1 deletions
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6
content/posts/teachingkotlin-part-1-classes-and-objects-and-everything-in-between.md
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@ -66,7 +66,7 @@ Kotlin:
```kotlin ```kotlin
class Person(val name: String, val age: Int = 18) { class Person(val name: String, val age: Int = 18) {
override fun toString() : String { override fun toString() : String {
// I know how cool this looks. I'll explore string templating differences in a future post, hold me to it :) // I'll go over string templates in a future post, hold me to it :)
return "Name=$name,age=$age" return "Name=$name,age=$age"
} }
} }
@ -95,3 +95,7 @@ class Person @JvmOverloads constructor(val name: String, val age: Int = 18) {
``` ```
Doing this will generate constructors similar to how we previously wrote in Java, to allow both Kotlin and Java callers to work. Doing this will generate constructors similar to how we previously wrote in Java, to allow both Kotlin and Java callers to work.
## Finality of classes
In Kotlin, all classes are final by default, and cannot be inherited while Java defaults to extensible classes. The `open` keyword marks Kotlin classes as extensible, and the `final` keyword does the opposite on Java. This is a behavior change that is confusing and undesirable to a lot of people, so Kotlin provides a compiler plugin to mark all classes as `open` by default. Check out the [`kotlin-allopen`](https://kotlinlang.org/docs/reference/compiler-plugins.html#all-open-compiler-plugin) page for more information about how to configure the plugin for your needs.