Welcome back! In today's lecture, we will delve into a critical concept within Scala: Primitive Data Type Conversion.

In software development, there can be scenarios where you need to manipulate data received in one format, typically from user inputs, and store or process it in a different format. For such occasions, it is essential to understand how to convert data types within Scala efficiently and safely.

By the end of this lesson, you will have learned the tools and techniques Scala provides for data type conversion. Additionally, you'll be able to perform these conversions safely while handling common errors efficiently. Let's get started!

Variables are used for storing and manipulating data in programming. Each variable has a specific data type that determines the kind of values it can hold. Sometimes, we need to move data across different types, and that's when data type conversion becomes essential.

Data type conversion, also known as typecasting, is the method of converting an entity from one data type to another.

Scala offers two broad categories of data type conversion:

• Implicit Conversion: Scala automatically performs this type of conversion when a smaller type is assigned to a more sizeable type size, albeit with a few exceptions.

• Explicit Conversion: As the name suggests, this type of conversion requires manual intervention and is frequently used when converting a larger data type to a smaller one.

Here's an example:

Scala
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1@main def run: Unit =
2  val myNumber = 5    // Declares a variable myNumber and initializes it with an integer value 5.
3  println(myNumber)   // Prints: 5
4  val myDouble = myNumber.toDouble    // Converts to Double
5  println(myDouble)   // Prints: 5.0

In this example, we declare a variable myNumber of type Int and value 5. We then explicitly convert it to a Double, resulting in myDouble. This illustrates explicit type casting in Scala.

In Scala, explicit conversions are mandatory where there could be misunderstandings or potential data loss. To facilitate this task, Scala provides specific built-in methods.

Before we dive into conversions, let's briefly explain the Short and Byte data types as they haven't been covered previously. A Short is a 16-bit signed integer, which can hold values from -32,768 to 32,767. A Byte is an 8-bit signed integer, capable of storing values from -128 to 127. These types are generally used when you need to conserve memory in large arrays by sacrificing some range or precision.

Here are some of the conversion functions that Scala offers:

• toByte: Converts value to Byte
• toShort: Converts value to Short
• toInt: Converts value to Int
• toLong: Converts value to Long
• toFloat: Converts value to Float
• toDouble: Converts value to Double
• toString: Converts value to String
• toChar: Converts a code to a Character

Let's see an example demonstrating these functions:

Scala
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1@main def run: Unit =
2  val number: Int = 65
3
4  println(number.toFloat) // prints "65.0"
5  println(number.toDouble) // prints "65.0"
6  println(number.toLong) // prints "65"
7  println(number.toChar) // prints "A"
8  println(number.toString) // prints "65"

Each line in this code snippet explicitly converts the Int value 65 to another data type using Scala's built-in functions. The original data type of number remains an Int.

Despite the simplicity of data type conversions, there are certain pitfalls to be noted — the most prominent being the loss of precision when converting from a type that can hold larger or more precise values to a smaller or less precise one.

Here's an example:

Scala
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1@main def run: Unit =
2  val myLargeNumber: Long = 100_000_000_000L
3  val mySmallNumber: Int = myLargeNumber.toInt
4  println(mySmallNumber)  // Outputs: -1215752192

In the above code, we tried to convert a large Long number into an Int, but the original number exceeds the maximum value an Int can hold, resulting in a faulty conversion. Therefore, understanding the limits of each data type is crucial before performing conversions.

Let's demonstrate a real-life scenario. In a shopping app that displays the total purchases of a user, the total might be calculated as a Double, but when it needs to be displayed in the app, it should be a String. Here, we use toString for conversion.

Scala
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1@main def run: Unit =
2  var totalCost = 295.75
3  var displayCost = totalCost.toString
4  println(displayCost)  // Outputs: "295.75"

Here, toString function is used to convert a Double totalCost into String displayCost.

Conversely, if there's a need to convert a character to its ASCII value, we would use the toInt method.

Scala
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1@main def run: Unit =
2  println('A'.toInt)  // Outputs: 65

This code converts a character A into its ASCII value - an integer 65.

Well done! Now, you have a thorough understanding of how to convert primitive data types in Scala! You've learned what data type conversion is, why it's essential, and how it's accomplished in Scala. Both implicit and explicit conversions have been covered, and you have a strong grasp of when each is needed. Also, we have illustrated real-world examples for all basic data types.

Safety is vital in data type conversion. It can lead to unexpected results and data loss if not executed properly. Ensure to indulge in reasoned and sensible conversions relevant to your program and manage potential errors correctly.

Now, it's time for practice to solidify these concepts. Complete the exercises that follow. Doing these exercises will take you one step closer to mastering Scala. Keep going; you're doing great!