kotlin - beginning

Author: PraGitHub

kotlin/.gitignore

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+*.jar
+/*.jar
+*/bin*

kotlin/essentials/control_flow.kt

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+package essentials.control_flow
+
+// Ternary equivalent is if and else
+// Switch-case equivaltent is when-in and default is given by else
+
+private fun ternary_and_case () {
+    val a = 100
+    val b = 10
+    val greater = if (a > b) a else b
+    println("Greater: ${greater}")
+
+    val exp = 10
+    val expGroup = when (exp) {
+        in 0..2 -> "Associate"
+        in 3..6 -> "Mid-Senior"
+        in 6..10 -> "Senior"
+        in 10..15 -> "Staff"
+        else -> "Senior-Staff"
+    }
+    println("Experience: ${exp}, Group: ${expGroup}")
+
+    val num = 5
+    when (num%2) {
+        0 -> println("${num} is even")
+        1 -> println("${num} is odd")
+    }
+}
+
+private fun max (a: Int, b: Int, c: Int): Int {
+    // if block returns something which is quite unique to kotlin
+    return (if (a > b && a > c) {
+            a
+        } else if (b > c) {
+            b
+        } else {
+            c
+        }
+    )
+}
+
+private fun loops () {
+     for (i in 1..10) {
+        print("${i} ")
+    }
+    println()
+    for (i in 10 downTo 1) {
+        print("${i} ")
+    }
+    println()
+    for (i in 1..10 step 2) {
+        print("${i} ")
+    }
+    println()
+    for (i in 10 downTo 1 step 2) {
+        print("${i} ")
+    }
+    println()
+
+    val animals = listOf("Lion", "Horse", "Elephant", "Camel", "Dog", "Tiger", "Leopard", "Rabbit", "Snake")
+
+    for (animal in animals) {
+        print("${animal} ")
+    }
+    println()
+    for ((i, animal) in animals.withIndex()) {
+        print("${i+1}: ${animal} ")
+    }
+    println()
+
+    var i = 0
+    val animal = "Dog"
+    while (i < animals.size) {
+        if (animals[i++].compareTo(animal) == 0){
+            println("${animal} exists");
+            break
+        }
+        if (i == animals.size) {
+            println("{animal} does not exist")
+        }
+    }
+}
+
+fun main () {
+    ternary_and_case()
+    println("Max(5, 9, 10) => ${max(5, 9, 10)}")
+    println("Max(10, 10000, 9052)3 => ${max(10, -10000, 90523)}")
+    loops()
+}

kotlin/essentials/run.bat

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+mkdir bin
+kotlinc types.kt -include-runtime -d bin\types.jar && java -jar bin\types.jar
+kotlinc strings.kt -include-runtime -d bin\strings.jar && java -jar bin\strings.jar
+kotlinc control_flow.kt -include-runtime -d bin\control_flow.jar && java -jar bin\control_flow.jar

kotlin/essentials/strings.kt

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+package essentials.strings
+
+fun main () {
+    var str1 = "prashanth"
+    var str2 = "kotlin"
+
+    println("${str1.compareTo(str2)}")
+    println("${str2.compareTo(str1)}")
+    println("${str1.compareTo(str1)}")
+
+    println("${str1}.get(2) => ${str1.get(2)}")
+    println("${str1}[2] => ${str1[2]}")
+    
+    println("${str1}.subSequence(2,5) => ${str1.subSequence(2,5)}")
+
+    for (char in str2) {
+        print("$char ")
+    }
+    println()
+
+    var raw_string = """
+    Hello World!
+    This is raw string from kotlin.
+                            - Prashanth
+    """
+    println(raw_string)
+}

kotlin/essentials/types.kt

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+package essentials.types
+
+// var: mutable
+// val: immutable
+
+private fun numbers_bool () {
+    var count: Int = 0
+
+    val number: Int = 42
+    val otherNumber = 43
+
+    val myLong: Long = 3000000000L
+    val myByte: Byte = 127
+    val myShort: Short = 32767
+
+    val myDouble: Double = 99.9
+    val myFloat: Float = 12.6F
+    val alsoDouble = 101.5
+
+    val asInt = alsoDouble.toInt()
+    val asFloat = myLong.toFloat()
+
+    val maxInt = 2_147_483_648
+
+    val myBoolean: Boolean = true
+
+    println("$count, $number, $otherNumber")
+    println("$myLong, $myByte, $myShort")
+    println("$myDouble, $myFloat, $alsoDouble")
+    println("$asInt, $asFloat, $alsoDouble, $maxInt")
+    println("$myBoolean ${!myBoolean}")
+}
+
+private fun char_strings () {
+    val myString: String = "prashanth"
+    val myChar: Char = 'P'
+
+    println("$myString, $myChar")
+
+    var myStringTemp: String
+    // using var as we need to assign something to myStringTemp several times
+    // if we use val then, we cannot assing things to myStringTemp more than once
+    // Error that we may get iwth val and multiple assignments: "error: val cannot be reassigned"
+    myStringTemp = myString.plus("_").plus(myChar.toString()); 
+    println("$myStringTemp")
+    myStringTemp = ""
+    myStringTemp = myString + "_" + myString;
+    println("$myStringTemp")
+    myStringTemp = ""
+    myStringTemp = "${myString}_${myString}";
+    println("$myStringTemp")
+}
+
+fun main () {
+    println("Hello World!")
+    numbers_bool();
+    char_strings();
+}