Introduction

In this tutorial, we will cover two important concepts in Kotlin: Type Conversion and Type Inference.

• Type Conversion refers to changing an entity of one data type into another. Kotlin strongly supports type checking, which means you cannot assign a value of one type to a variable of another type. If you need to do this, you must explicitly convert it to another type.

• Type Inference is a feature of Kotlin where the compiler detects the data type of a variable on its own. You don't need to declare the type of a variable explicitly; Kotlin's compiler does that job for you.

By the end of this tutorial, you will:
- Understand Type Conversion and Type Inference in Kotlin
- Learn how to convert one data type to another
- Understand how Kotlin infers the type of a variable
- Practice with examples to reinforce your understanding

The prerequisites for this tutorial include basic knowledge of Kotlin, including understanding of data types and variables.

Step-by-Step Guide

Type Conversion

In Kotlin, conversions are done by using helper functions. For example, to convert an integer to a string, we use the toString() method, and to convert a string to an integer, we use the toInt() method.

Here's an example:

var number: Int = 5
var numberToString: String = number.toString()

In this example, numberToString will have a value of "5", not 5.

Type Inference

Type inference in Kotlin means that the compiler automatically infers the type of the variable from the initializer expression.

Here's an example:

var name = "John"

In this example, we didn't explicitly define the type of the name variable. However, Kotlin's compiler can infer that the name variable is a String because it's initialized with a String value.

Code Examples

Type Conversion

// Define an integer
var integer: Int = 10

// Convert integer to a String
var string: String = integer.toString()

// The output will be: 10
println(string)

// Define a String
var str: String = "20"

// Convert String to an integer
var int: Int = str.toInt()

// The output will be: 20
println(int)

In the above example, we first defined an integer and converted it to a string. Then, we defined a string and converted it to an integer. The println() function is used to print the result.

Type Inference

// Define a variable with a Double value
var number = 10.0

// The output will be: Double
println(number::class.simpleName)

// Define a variable with a String value
var name = "John"

// The output will be: String
println(name::class.simpleName)

In this example, we defined two variables without explicitly stating their data types. Kotlin's compiler inferred their types based on their initial values.

Summary

In this tutorial, we learned about type conversion and type inference in Kotlin. We saw how to convert one data type to another, and how Kotlin's compiler infers the type of a variable. We also explored practical examples to solidify your understanding.

Next, you should practice these concepts with different data types and variables. You can refer to the Kotlin documentation for more details and examples.

Practice Exercises

1. Convert a double to a string, and print the result.
2. Convert a string that represents a boolean value (e.g., "true") to a boolean.
3. Define a variable with an integer value, and let Kotlin infer its type.

Here are the solutions:

// Solution to Exercise 1
var double: Double = 10.5
var string: String = double.toString()
println(string)  // Output: 10.5

// Solution to Exercise 2
var str: String = "true"
var bool: Boolean = str.toBoolean()
println(bool)  // Output: true

// Solution to Exercise 3
var number = 10
println(number::class.simpleName)  // Output: Int

In these exercises, you practiced converting different data types to another and letting Kotlin infer the type of a variable. Continue practicing these concepts to get a firm understanding. Happy Kotlin learning!