part1

src/i_introduction/_0_Hello_World/n00Start.kt

@@ -25,5 +25,5 @@ fun todoTask0(): Nothing = TODO(
 )
 
 fun task0(): String {
-    return todoTask0()
+    return "OK"
 }

src/i_introduction/_10_Object_Expressions/n10ObjectExpressions.kt

@@ -5,19 +5,29 @@ import util.doc10
 import java.util.*
 
 fun todoTask10(): Nothing = TODO(
-    """
+        """
         Task 10.
         Read about object expressions that play the same role in Kotlin as anonymous classes in Java.
 
         Add an object expression that provides a comparator to sort a list in a descending order using 'java.util.Collections' class.
         In Kotlin you use Kotlin library extensions instead of java.util.Collections,
         but this example is still a good demonstration of mixing Kotlin and Java code.
     """,
-    documentation = doc10()
+        documentation = doc10()
 )
 
 fun task10(): List<Int> {
     val arrayList = arrayListOf(1, 5, 2)
-    Collections.sort(arrayList, todoTask10())
+    Collections.sort(arrayList, { x, y -> y-x})
+    fun xxx(x: Int, y: Int): Int {
+        return y - x
+    }
+    Collections.sort(arrayList, fun(x: Int, y: Int): Int {
+        return y - x
+    })
     return arrayList
+}
+
+fun xxx(x: Int, y: Int): Int {
+    return y - x
 }

src/i_introduction/_11_SAM_Conversions/n11SAMConversions.kt

@@ -15,6 +15,6 @@ fun todoTask11(): Nothing = TODO(
 
 fun task11(): List<Int> {
     val arrayList = arrayListOf(1, 5, 2)
-    Collections.sort(arrayList, { x, y -> todoTask11() })
+    Collections.sort(arrayList, { x, y -> y - x })
     return arrayList
 }

src/i_introduction/_12_Extensions_On_Collections/n12ExtensionsOnCollections.kt

@@ -17,7 +17,7 @@ fun todoTask12(): Nothing = TODO(
 )
 
 fun task12(): List<Int> {
-    todoTask12()
-    return arrayListOf(1, 5, 2)
+
+    return arrayListOf(1, 5, 2).sortedDescending()
 }
 

src/i_introduction/_1_Java_To_Kotlin_Converter/n01JavaToKotlinConverter.kt

@@ -14,5 +14,16 @@ fun todoTask1(collection: Collection<Int>): Nothing = TODO(
 
 
 fun task1(collection: Collection<Int>): String {
-    todoTask1(collection)
+    val sb = StringBuilder()
+    sb.append("{")
+    val iterator = collection.iterator()
+    while (iterator.hasNext()) {
+        val element = iterator.next()
+        sb.append(element)
+        if (iterator.hasNext()) {
+            sb.append(", ")
+        }
+    }
+    sb.append("}")
+    return sb.toString()
 }

src/i_introduction/_2_Named_Arguments/n02NamedArguments.kt

@@ -24,6 +24,6 @@ fun todoTask2(): Nothing = TODO(
     references = { collection: Collection<Int> -> task1(collection); collection.joinToString() })
 
 fun task2(collection: Collection<Int>): String {
-    todoTask2()
-    return collection.joinToString()
+
+    return collection.joinToString(prefix="{",postfix="}")
 }

src/i_introduction/_3_Default_Arguments/n03DefaultArguments.kt

@@ -14,12 +14,15 @@ fun todoTask3(): Nothing = TODO(
     documentation = doc2(),
     references = { name: String -> JavaCode3().foo(name); foo(name) })
 
-fun foo(name: String): String = todoTask3()
+fun foo(name: String, number: Int=42, toUpperCase : Boolean=false): String  {
+   if(toUpperCase == true )  {  return  name.toUpperCase() + number }  else { return  name + number}
+}
+
 
 fun task3(): String {
-    todoTask3()
-//    return (foo("a") +
-//            foo("b", number = 1) +
-//            foo("c", toUpperCase = true) +
-//            foo(name = "d", number = 2, toUpperCase = true))
+
+  return (foo("a") +
+          foo("b", number = 1) +
+          foo("c", toUpperCase = true) +
+          foo(name = "d", number = 2, toUpperCase = true))
 }

src/i_introduction/_4_Lambdas/n04Lambdas.kt

@@ -22,4 +22,4 @@ fun todoTask4(collection: Collection<Int>): Nothing = TODO(
     documentation = doc4(),
     references = { JavaCode4().task4(collection) })
 
-fun task4(collection: Collection<Int>): Boolean = todoTask4(collection)
+fun task4(collection: Collection<Int>): Boolean =collection.any{ x -> x%2==0}

src/i_introduction/_5_String_Templates/n05StringTemplates.kt

@@ -35,4 +35,4 @@ fun todoTask5(): Nothing = TODO(
     documentation = doc5(),
     references = { getPattern(); month })
 
-fun task5(): String = todoTask5()
+fun task5(): String =  """\d{2} ${month} \d{4}"""

src/i_introduction/_6_Data_Classes/n06DataClasses.kt

@@ -15,10 +15,9 @@ fun todoTask6(): Nothing = TODO(
     references = { JavaCode6.Person("Alice", 29) }
 )
 
-class Person
+ data class Person(var name: String , var age: Int )
 
 fun task6(): List<Person> {
-    todoTask6()
-    return listOf(/*Person("Alice", 29), Person("Bob", 31)*/)
+    return listOf(Person("Alice", 29), Person("Bob", 31))
 }
 

src/i_introduction/_7_Nullable_Types/n07NullableTypes.kt

@@ -25,7 +25,13 @@ fun todoTask7(client: Client?, message: String?, mailer: Mailer): Nothing = TODO
 fun sendMessageToClient(
     client: Client?, message: String?, mailer: Mailer
 ) {
-    todoTask7(client, message, mailer)
+    if (client == null || message == null) return
+
+    val personalInfo = client.personalInfo ?: return
+
+    val email = personalInfo.email ?: return
+
+    mailer.sendMessage(email, message)
 }
 
 class Client(val personalInfo: PersonalInfo?)

src/i_introduction/_8_Smart_Casts/n08SmartCasts.kt

@@ -12,8 +12,8 @@ class Sum(val left: Expr, val right: Expr) : Expr()
 
 fun eval(e: Expr): Int =
     when (e) {
-        is Num -> todoTask8(e)
-        is Sum -> todoTask8(e)
+        is Num -> (e as Num).value
+        is Sum -> eval(e.left) + eval(e.right)
     }
 
 fun todoTask8(expr: Expr): Nothing = TODO(

src/i_introduction/_9_Extension_Functions/n09ExtensionFunctions.kt

@@ -29,7 +29,7 @@ fun todoTask9(): Nothing = TODO(
 
 data class RationalNumber(val numerator: Int, val denominator: Int)
 
-fun Int.r(): RationalNumber = todoTask9()
-fun Pair<Int, Int>.r(): RationalNumber = todoTask9()
+fun Int.r(): RationalNumber = RationalNumber( this,1)
+fun Pair<Int, Int>.r(): RationalNumber =RationalNumber( first,second)