Kotlin is a renowned programming language known for its clear syntax and feature-rich functionalities. It is typically used for mobile application development and Java Virtual Machine (JVM) projects.
groupBy() methodThe groupBy() function groups elements from a collection based on a specific key or criterion. It is mainly used for data manipulation and organization as it offers a streamlined way to categorize and manage data efficiently.
The syntax of the groupBy() method is given below:
fun <K, V> Iterable<T>.groupBy(keySelector: (T) -> K): Map<K, List<T>>
T is the type of elements in the collection.
K is the type of keys used for grouping.
V is the type of value associated with each key.
keySelector is a lambda function that defines the key for grouping elements.
Note: Make sure you have Kotlin installed. To learn more about the Kotlin installation on your system, click here.
Let's look at the code below to demonstrate the use of the groupBy() method.
Suppose we have a list of employees with their names and departments and want to group them by department.
data class Employee(val name: String, val department: String)fun main() {val employees = listOf(Employee("Alice", "HR"),Employee("Bob", "Engineering"),Employee("Charlie", "HR"),Employee("David", "Sales"),Employee("Eva", "Engineering"))val groupedByDepartment = employees.groupBy { it.department }println(groupedByDepartment)}
Line 1: Firstly, we define a data class Employee to represent each employee's name and department as string variables.
Line 3–10: Next, we create a list of five Employee instances named employees.
Line 12: Here, we use the groupBy() method on the employees list and pass a lambda function as the key selector.
Line 14: Finally, we print the resulting groupedByDepartment map that contains department names as keys and lists of employees as values.
Upon execution, the code categorizes employees based on their departments. The resulting map uses department names as keys, each of which is linked to a list of employees from that department.
The output looks something like this:
{HR=[Employee(name=Alice, department=HR), Employee(name=Charlie, department=HR)],Engineering=[Employee(name=Bob, department=Engineering), Employee(name=Eva, department=Engineering)],Sales=[Employee(name=David, department=Sales)]}
Therefore, Kotlin's groupBy() function is vital for organizing and categorizing data depending on specific criteria. It can organize raw data into groupings and improves data analysis, reporting, and processing. Developers may use this function to automate data processing operations and write more efficient and understandable code.
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