If-Else Chain

Understanding Else If

It is often the case when we have multiple conditions and for each separate condition a separate code block should be executed. That's where the else if statement comes into play.

Let's first take a look at the flowchart which combines if, else if and else:

Here's an example to make things clear. Suppose I want to determine whether I have enough money on the balance (balance) to buy a certain number of books (booksNumber) given their price (bookPrice). If my balance is greater than or equal to the total cost of the books (totalCost), I can afford them. Moreover, if the difference between my balance and the total cost of the books is less than or equal to 100, a discount can be made and I'll be able to buy them. If the difference is greater, then I cannot afford the books.

Main


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object Main {
  def main(args: Array[String]): Unit = {
    val bookPrice = 120
    val booksNumber = 25
    var totalCost = bookPrice * booksNumber
    var balance = 2890
    if (balance >= totalCost) {
      balance -= totalCost
      println("I can afford them")
    }
    else if (totalCost - balance <= 100) {
      balance = 0
      println("A discount can be made")
    }
    else {
      println("I cannot afford them ")
    }
    println("The current balance is " + balance)
  }
}

More Else If

In fact, you can have an arbitrary number of else if statements in case you want to execute different code for different conditions. Basically, you just stack them vertically in the desired order like this:

Main


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    if (condition1) {
      // code to execute
    }
    else if (condition2) {
      // code to execute
    }
    else if (condition3) {
      // code to execute
    }
    // You can as many conditions as you want
    else {
      // code to execute
    }

As you can see, the approach is rather simple and straightforward.

Nested Conditional Statements

As a matter of fact, the code blocks within conditional statements (if, else if or else) can also contain other conditional statements which are called nested conditional statements. The level of nesting can also be arbitrarily large.

Main


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if (condition1) {
	// The nesting can be arbitrarily deep
	if (...) {
		// code to execute
	}
	else if (...) {
    	//code to execute
    	if (...) {
        	//code to execute
        }
	}
    else (...) {
    	//code to execute
    }
}
else if (condition2) {
	if (...) {
		// code to execute
	}
}
else {
	// code to execute
}

Overall, using else if we can make our code much more flexible by adding more alternatives to the conditions.

Everything was clear?

Thanks for your feedback!

Section 3. Chapter 2