Kotlin Basics - Android Development Lesson 1

Study Notes

Open IntelliJ IDEA and create a new project.
Utilize REPL (Read-Eval-Print-Loop) to run Kotlin code.
Create functions, such as printHello(), and execute using Control+Enter (or Command+Enter on Mac).

Kotlin treats numbers as primitives but allows method calls, e.g., 2.times(3) returns 6.
Other methods:
- 3.5.plus(4) gives 7.5
- 2.4.div(2) yields 1.2

Integer Types:
- Long: 64 bits, range -2^63 to 2^63-1
- Int: 32 bits, range -2^31 to 2^31-1
- Short: 16 bits, range -32768 to 32767
- Byte: 8 bits, range -128 to 127
Floating-point Types:
- Double: 64 bits, precision of 16-17 significant digits.
- Float: 32 bits, precision of 6-7 significant digits.
Other Types:
- Char: 16-bit Unicode character
- Boolean: 8 bits, can be true or false.

For Loops: Simplifies iteration over collections without manual index management.
Sample Usage:
- Iterate over an array of pets with syntax for (element in pets).
- Access both index and element using for ((index, element) in pets.withIndex()).
While Loops: Useful for repeating actions until a condition is met. E.g., incrementing a counter within a limit.
Repeat Loops: Execute a block of code a certain number of times, e.g., repeat(2) { print("Hello!") }.

Lists:
- Ordered collections; allow duplicates.
- Immutable lists created using listOf(), e.g., val instruments = listOf("trumpet", "piano").
- Mutable lists created using mutableListOf(), which allows element changes.
Arrays:
- Fixed-size collections that can store multiple items of the same or mixed types.
- Create arrays using arrayOf(), e.g., val pets = arrayOf("dog", "cat").
- Combine arrays with the + operator, e.g., val combined = numbers2 + numbers.

By default, Kotlin variables cannot be null, preventing null-pointer exceptions.
A variable can be declared nullable using ?, e.g., var numberOfBooks: Int? = null.
Safe call operator (?) checks for null before proceeding, and the Elvis operator (?:) can provide default values.
Avoid setting variables to null as it may lead to unwanted consequences.

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