Slack Kotlin Interview Questions

1. Explain lambda syntax in Kotlin including it parameter, trailing lambdas, and capturing variables.

Difficulty: MediumType: SubjectiveTopic: Lambdas

Lambda syntax in Kotlin uses curly braces with optional parameters before arrow and body after like open curly x comma y arrow x plus y close curly, but if there's only one parameter you can omit it and use the implicit it variable. Lambdas can capture variables from their surrounding scope making them closures, and captured variables can be modified inside the lambda unlike Java's effectively final requirement. Trailing lambda syntax allows moving the last lambda parameter outside parentheses for better readability like list dot filter open paren close paren open curly it greater 5 close curly, and if the lambda is the only argument you can omit the parentheses entirely. This makes DSL-like code and builder patterns very readable in Kotlin. Understand that lambdas are compiled to function objects or inlined depending on context, and using inline functions can eliminate lambda overhead for performance-critical code. Lambda receivers like String dot open paren close paren arrow Unit enable DSL creation where this refers to the receiver type inside the lambda body.

2. Explain the difference between val and var with examples and when to use each.

Difficulty: EasyType: SubjectiveTopic: Variables

Use val for read-only variables that are assigned once and never change, like val pi equals 3.14 or val name equals John, which is similar to final in Java and promotes immutability making code safer and more predictable. Use var for mutable variables that need to be reassigned, like var counter equals 0 followed by counter plus plus, necessary for loops, accumulators, or state that legitimately changes. Prefer val as the default choice and only use var when you genuinely need to mutate the variable, as immutability prevents accidental changes, makes code easier to reason about especially in concurrent environments, and aligns with functional programming principles. The Kotlin style guide recommends using val whenever possible, and the IDE even suggests converting var to val when it detects the variable is never reassigned, helping enforce this best practice.

3. What is the syntax for a lambda expression in Kotlin?

Difficulty: EasyType: MCQTopic: Lambdas

Kotlin lambda expressions are enclosed in curly braces with parameters before the arrow and the body after, like val sum equals open curly x comma y arrow x plus y close curly. If the lambda has a single parameter, you can use the implicit it variable instead of declaring the parameter name. Lambdas can capture variables from their surrounding scope, and if a lambda is the last parameter of a function call, it can be placed outside the parentheses for better readability. This syntax is concise and integrates seamlessly with Kotlin's higher-order functions.

4. What is the difference between val and var in Kotlin?

Difficulty: EasyType: MCQTopic: Variables

In Kotlin, val declares a read-only variable that can be assigned only once, similar to final in Java, promoting immutability and safer code. var declares a mutable variable that can be reassigned multiple times. Using val is preferred whenever possible as it makes code more predictable and thread-safe by preventing accidental modifications. The Kotlin compiler encourages using val by showing warnings when var could be replaced with val, helping developers write more functional and immutable code.

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Quick overview

Slack · Kotlin questions (4)

1. Explain lambda syntax in Kotlin including it parameter, trailing lambdas, and capturing variables.

Continue your preparation

2. Explain the difference between val and var with examples and when to use each.

3. What is the syntax for a lambda expression in Kotlin?

4. What is the difference between val and var in Kotlin?

Master Interviews Anywhere, Anytime

Slack Kotlin interview questions

Quick overview

1. Explain lambda syntax in Kotlin including it parameter, trailing lambdas, and capturing variables.

Continue your preparation

2. Explain the difference between val and var with examples and when to use each.

3. What is the syntax for a lambda expression in Kotlin?

4. What is the difference between val and var in Kotlin?

Master Interviews
Anywhere, Anytime