Constant values with const val in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does <code>const val</code> mean in Kotlin?

<p><code>const val</code> declares a compile-time constant. It means the value is fixed and known when the program is compiled, not changed at runtime.</p>

beginner

Where can <code>const val</code> be used in Kotlin?

<p><code>const val</code> can only be used at the top level or inside an <code>object</code>. It cannot be used inside regular classes or functions.</p>

intermediate

Why use <code>const val</code> instead of just <code>val</code>?

<p><code>const val</code> is a compile-time constant, so it can be inlined and used in annotations. <code>val</code> is a runtime constant and cannot be used in these cases.</p>

beginner

Example: How to declare a constant string with <code>const val</code>?

<pre>object Constants {
    const val APP_NAME = "MyApp"
}</pre><p>This creates a constant string <code>APP_NAME</code> accessible as <code>Constants.APP_NAME</code>.</p>

intermediate

Can <code>const val</code> hold complex objects or only primitives and strings?

<p><code>const val</code> can only hold primitive types (like <code>Int</code>, <code>Double</code>) and <code>String</code>. It cannot hold objects or types that require runtime initialization.</p>

Which of the following is true about const val in Kotlin?

A It is a compile-time constant and can be used in annotations.

B It can be declared inside any function.

C It can hold any object type.

D It can be changed after initialization.

const val is a compile-time constant, usable in annotations. It cannot be declared inside functions, cannot hold objects, and cannot be changed.

Where can you declare a const val in Kotlin?

A Inside a regular class.

B Inside a function.

C Inside an <code>object</code> or at the top level.

D Inside a <code>var</code> declaration.

const val must be declared at the top level or inside an object. It cannot be inside functions or regular classes.

What types of values can const val hold?

A Only nullable types.

B Only primitive types and strings.

C Only collections like lists or maps.

D Any object type.

const val can only hold primitive types (like Int, Boolean) and String.

Why might you choose const val over val?

A Because <code>const val</code> values are known at compile time and can be inlined.

B Because <code>const val</code> values are mutable.

C Because <code>val</code> can only be used inside functions.

D Because <code>val</code> cannot hold strings.

const val values are compile-time constants and can be inlined, making them more efficient and usable in annotations.

Which of these is a valid const val declaration?

A const val list = listOf(1, 2, 3)

B const val name = getName()

C const val user = User()

D const val PI = 3.14

Only primitive or string literals can be const val. Calling functions or creating objects is not allowed.

Explain what const val means in Kotlin and where you can use it.

Think about when the value is fixed and where Kotlin allows this declaration.

Describe the difference between const val and val in Kotlin.

Consider when the value is known and how Kotlin treats each.