Creating instances without new keyword in Kotlin - Performance & Efficiency

Time Complexity: Creating instances without new keyword

O(n)

Understanding Time Complexity

We want to understand how the time it takes to create objects changes as we create more of them without using the new keyword.

How does the cost grow when making many instances this way?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

class Person(val name: String)

fun createPeople(names: List): List {
    return names.map { Person(it) }
}
    

This code creates a list of Person objects from a list of names without using the new keyword explicitly.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Creating a Person instance for each name in the list.
• How many times: Once for each element in the input list names.

How Execution Grows With Input

Each name causes one new Person to be created, so the work grows directly with the number of names.

Input Size (n)	Approx. Operations
10	10 creations
100	100 creations
1000	1000 creations

Pattern observation: The number of operations grows in a straight line with input size.

Final Time Complexity

Time Complexity: O(n)

This means the time to create all instances grows directly in proportion to how many you make.

Common Mistake

[X] Wrong: "Creating instances without the new keyword is faster or slower in a way that changes time complexity."

[OK] Correct: The keyword new is just syntax; the actual work of creating each object still happens once per item, so time grows the same way.

Interview Connect

Understanding how object creation scales helps you reason about performance in real apps, especially when working with collections and data transformations.

Self-Check

"What if we changed map to a recursive function creating instances? How would the time complexity change?"