{
"cells": [
{
"cell_type": "code",
"execution_count": 1,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Hello World\n"
]
}
],
"source": [
"// simple print to stdout\n",
"\n",
"println(\"Hello World\")"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"stdin:Hello World\n",
"Hello World\n"
]
}
],
"source": [
"// simple read from stdin\n",
"\n",
"println(readLine())"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Variable\n",
"\n",
"var x = 1\n",
"x = 2\n",
"println(x)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// constant\n",
"\n",
"val y = 9\n",
"// y = 4\n",
"println(y)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Different types of elements in Kotlin\n",
"\n",
"fun kotlinAndJavaType(value: Any): String {\n",
" return \"Kotlin: \" + value::class.simpleName + \" | Java: \" + value.javaClass.typeName\n",
"}\n",
"\n",
"println(kotlinAndJavaType(3))\n",
"println(kotlinAndJavaType(3.4))\n",
"println(kotlinAndJavaType(\"something\"))\n",
"println(kotlinAndJavaType(listOf(1, 2, 3)))\n",
"println(kotlinAndJavaType(mapOf(1 to \"One\", 2 to \"Two\", 3 to \"Three\")))\n",
"println(kotlinAndJavaType(setOf(1, 2, 3)))"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Immutability\n",
"\n",
"val lst = listOf(1, 2, 3)\n",
"val lst2 = lst.reversed()\n",
"val lst3 = listOf(6, 7, 8) + lst + listOf(9, 10)\n",
"println(lst)\n",
"println(lst2)\n",
"println(lst3)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Mutability\n",
"\n",
"val lst4 = mutableListOf(1, 2, 3)\n",
"println(lst4)\n",
"lst4.add(4)\n",
"println(lst4)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Nullability and Null safety\n",
"\n",
"// val nonNullable: Int = null\n",
"// println(nonNullable)\n",
"\n",
"val nullable: Int? = null\n",
"println(nullable)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Conditional statement\n",
"\n",
"print(\"Enter your age: \")\n",
"val age = Integer.parseInt(readLine())\n",
"if (age >= 18)\n",
" println(\"You are allowed to drink\")\n",
"else\n",
" println(\"It's illegal for you to drink\")"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// Conditional expression\n",
"\n",
"print(\"Enter your age: \")\n",
"val age = Integer.parseInt(readLine())\n",
"val allowedToDrink = if (age >= 18) \"Allowed to drink\" else \"It's illegal for you to drink\"\n",
"println(allowedToDrink)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// when (somewhat pattern matching, somewhat switch)\n",
"\n",
"fun checkIfIsValidNumberGreaterThan10(value: Int): String {\n",
" val validNumbers = listOf(13, 17, 19)\n",
" when(value) {\n",
" in 1..10 -> return \"x is in the range\"\n",
" in validNumbers -> return \"x is valid\"\n",
" !in 10..20 -> return \"x is outside the range\"\n",
" else -> return \"none of the above\"\n",
" }\n",
"}\n",
"checkIfIsValidNumberGreaterThan10(Integer.parseInt(readLine()))"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// functions as set of statements\n",
"\n",
"fun squareAsStatement(x: Int): Int {\n",
" return x * x\n",
"}\n",
"squareAsStatement(4)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// functions as expressions\n",
"\n",
"fun squareAsExpression(x: Int) = x * x\n",
"squareAsExpression(4)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// functions with default args\n",
"\n",
"fun increment(x: Int, by_: Int=1) = x + by_\n",
"println(increment(5))\n",
"println(increment(5, by_=3))"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// functions to be used as infix\n",
"\n",
"infix fun Int.toThePower(power: Int): Int = if (power == 1) this else this * (this toThePower power -1)\n",
"2 toThePower 3"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// lambdas as shorthand functions\n",
"\n",
"val incrementLambda = { i: Int -> i + 1 }\n",
"incrementLambda(5)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// inline function using lambda\n",
"\n",
"import java.io.File\n",
"inline fun withLock(name: String, block: () -> Unit) {\n",
" while (File(\"${name}.lock\").exists())\n",
" Thread.sleep(1000)\n",
" block()\n",
" File(\"${name}.lock\").delete()\n",
"}\n",
"\n",
"withLock(\"write-to-shared-file\") {\n",
" println(\"access 1\")\n",
"}\n",
"\n",
"withLock(\"write-to-shared-file\") {\n",
" println(\"access 2\")\n",
"}\n",
"withLock(\"write-to-shared-file\") {\n",
" println(\"access 3\")\n",
"}\n",
"withLock(\"write-to-shared-file\") {\n",
" println(\"access 4\")\n",
"}\n",
"withLock(\"write-to-shared-file\") {\n",
" println(\"access 5\")\n",
"}"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// simple class\n",
"\n",
"data class Product(val name: String, val cost: Int)\n",
"interface Totalable {\n",
" fun total(): Int\n",
"}\n",
"class Cart(val products: List<Product>) : Totalable {\n",
" override fun total(): Int {\n",
" return products.fold(0) { total, product -> total + product.cost }\n",
" }\n",
"}\n",
"\n",
"val products = listOf(Product(\"iPhone\", 1000), Product(\"iPhone Charger\", 3000))\n",
"println(products)\n",
"val cart = Cart(products)\n",
"println(cart.total())"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// objects\n",
"\n",
"import java.sql.*\n",
"object loggedInUser {\n",
" var userName: String?=null\n",
"}\n",
"println(loggedInUser.userName)\n",
"loggedInUser.userName = \"Someone\"\n",
"println(loggedInUser.userName)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// ranges\n",
"\n",
"println(kotlinAndJavaType(1..10))\n",
"println(kotlinAndJavaType(1 until 10))\n",
"println(1..10)\n",
"println(10..1)\n",
"println(1 until 10)\n",
"println(20 downTo 1 step 2)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// looping\n",
"\n",
"for (x in 20 downTo 1 step 2) {\n",
" println(x)\n",
"}"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"// map -> filter -> reduce\n",
"val listOf100Elements = (1..100 step 1).toList()\n",
"println(\"listOf100Elements: ${listOf100Elements}\")\n",
"println()\n",
"val squareOfAll200Elements = listOf100Elements.map { num -> num * 2 }\n",
"println(\"squareOfAll200Elements: ${squareOfAll200Elements}\")\n",
"println()\n",
"val thoseWithNumbersDivisibleBy4FilteredOut = squareOfAll200Elements.filter { num -> num % 4 != 0 }\n",
"println(\"thoseWithNumbersDivisibleBy4FilteredOut: ${thoseWithNumbersDivisibleBy4FilteredOut}\")\n",
"println()\n",
"val sumOfAllThoseNumbers = thoseWithNumbersDivisibleBy4FilteredOut.reduce { acc, num -> acc + num }\n",
"println(\"sumOfAllThoseNumbers: ${sumOfAllThoseNumbers}\")\n",
"println()"
]
}
],
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"kernelspec": {
"display_name": "Kotlin",
"language": "kotlin",
"name": "kotlin"
},
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"file_extension": ".kt",
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