KotlinHow-ToBeginner · 3 min read

How to Use Comparison Operators in Kotlin: Syntax and Examples

In Kotlin, you use == to check if two values are equal and != to check if they are not equal. Other comparison operators like <, <=, >, and >= compare values to see if one is less than, less or equal, greater than, or greater or equal to another.

📐

Syntax

Kotlin provides simple comparison operators to compare values. Here are the main ones:

==: Checks if two values are equal.
!=: Checks if two values are not equal.
<: Checks if the left value is less than the right value.
<=: Checks if the left value is less than or equal to the right value.
>: Checks if the left value is greater than the right value.
>=: Checks if the left value is greater than or equal to the right value.

These operators return a Boolean value: true or false.

kotlin

val a = 5
val b = 10

val isEqual = (a == b)       // false
val isNotEqual = (a != b)    // true
val isLess = (a < b)         // true
val isLessOrEqual = (a <= b) // true
val isGreater = (a > b)      // false
val isGreaterOrEqual = (a >= b) // false

💻

Example

This example shows how to use comparison operators in Kotlin to compare two numbers and print the results.

kotlin

fun main() {
    val x = 7
    val y = 12

    println("x == y: ${x == y}")
    println("x != y: ${x != y}")
    println("x < y: ${x < y}")
    println("x <= y: ${x <= y}")
    println("x > y: ${x > y}")
    println("x >= y: ${x >= y}")
}

Output

x == y: false x != y: true x < y: true x <= y: true x > y: false x >= y: false

⚠️

Common Pitfalls

One common mistake is using = instead of == for comparison. In Kotlin, = is for assignment, not comparison.

Another pitfall is confusing == with ===. The == operator checks structural equality (if values are equal), while === checks referential equality (if two variables point to the same object).

kotlin

fun main() {
    val a = 5
    val b = 5

    // Wrong: assignment instead of comparison
    // if (a = b) { // This will cause a compile error
    //     println("Equal")
    // }

    // Correct: use == for comparison
    if (a == b) {
        println("a and b are equal")
    }

    // Referential equality example
    val str1 = "hello"
    val str2 = "hello"
    println(str1 == str2)  // true, values are equal
    println(str1 === str2) // true or false depending on JVM optimizations
}

Output

a and b are equal true true

📊

Quick Reference

Operator	Meaning	Example	Result
==	Checks if two values are equal	5 == 5	true
!=	Checks if two values are not equal	5 != 3	true
<	Checks if left is less than right	3 < 5	true
<=	Checks if left is less or equal to right	5 <= 5	true
>	Checks if left is greater than right	7 > 2	true
>=	Checks if left is greater or equal to right	7 >= 7	true

✅

Key Takeaways

Use == and != to check if values are equal or not equal in Kotlin.

Use <, <=, >, >= to compare numeric or comparable values.

Remember = is for assignment, not comparison; use == for checking equality.

== checks if values are equal, === checks if two references point to the same object.

Comparison operators return Boolean values: true or false.