Best Scala Programming Guides to Buy in October 2025
Programming in Scala Fifth Edition
Functional Programming in Scala, Second Edition
Programming Scala: Scalability = Functional Programming + Objects
Programming in Scala
Functional Programming in Scala
Scala for the Impatient
In Scala, you can skip an iteration in a for-loop using the continue keyword. This keyword allows you to bypass the rest of the current iteration and move on to the next one.
Here's an example of how you can use continue in a for-loop in Scala:
for (i <- 1 to 5) { if (i == 3) { // Skipping iteration when i is equal to 3 continue // This is the "continue" keyword in Scala } println(i) }
In this example, the for-loop iterates from 1 to 5. When i is equal to 3, the continue keyword is used to skip the remainder of the current iteration. As a result, the number 3 is not printed, and the loop moves on to the next iteration.
You can use continue within any condition or logical expression to control whether an iteration should be skipped or not.
Keep in mind that the continue keyword is not directly supported in Scala like it is in some other programming languages. Instead, you can simulate the behavior of continue by using an if statement or other control flow constructs to skip the code that should be ignored in a particular iteration.
What is an iterator in Scala?
An iterator in Scala is an object that allows iteration over a collection of elements one at a time. It provides methods such as next and hasNext to retrieve the next element and check if there are more elements available in the collection, respectively.
The Iterator trait is the base trait for all iterators in Scala. It is implemented by various collections in the Scala standard library including List, Set, and [Map](https://topminisite.com/blog/how-to-populate-a-mutable-map-using-a-loop-in-scala). Additionally, Scala provides convenience methods like iterator on various collection types to convert them into an iterator.
Iterators in Scala are often used in functional programming to perform various operations on collections, such as filtering, mapping, and reducing elements. They are particularly useful when working with large collections, as they allow for lazy evaluation, avoiding unnecessary computation.
What is the purpose of a nested for-loop in Scala?
The purpose of a nested for-loop in Scala is to iterate over a collection of elements multiple times, where the inner loop is executed for each iteration of the outer loop.
This is useful when you have a multi-dimensional or nested data structure, such as a 2D array, a list of lists, or a collection of tuples. It allows you to access and process each element in a systematic way, considering both the outer and inner dimensions.
For example, consider a 2D array representing a grid:
val grid = Array( Array(1, 2, 3), Array(4, 5, 6), Array(7, 8, 9) )
You can use nested for-loops to iterate over each element in the grid like this:
for (row <- grid) { for (cell <- row) { println(cell) } }
This will output:
1 2 3 4 5 6 7 8 9
Nested for-loops provide a way to efficiently traverse and process complex data structures by breaking down the problem into simpler iterations.
How to filter elements in a for-loop in Scala?
In Scala, you can use the if statement within a for loop to filter elements. Here's an example:
val numbers = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
for (n <- numbers if n % 2 == 0) { println(n) }
In this example, the for loop iterates over the numbers list and the if statement filters out only the even numbers. The filtered elements are then printed.
Output:
2 4 6 8 10
You can combine multiple filtering conditions using multiple if statements:
val numbers = List(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
for (n <- numbers if n % 2 == 0 if n > 5) { println(n) }
In this case, the for loop will only print the even numbers greater than 5.
Output:
6 8 10
Note that using a for loop for filtering elements can be less efficient for large collections. In such cases, it's recommended to use higher-order functions like filter, map, and reduce provided by Scala's collections library.