66 lines
1.7 KiB
Plaintext
66 lines
1.7 KiB
Plaintext
== Why is this an issue?
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In Kotlin, `==` means structural equality and maps to the left-side term's `equals()` function.
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It is, therefore, redundant to call `equals()` as a function.
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Also, `==` is more general than `equals()` because it allows either of both operands to be `null`.
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Developers using `equals()` instead of `==` is often the result of adapting
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styles from other languages like Java, where `==` means reference equality.
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=== What is the potential impact?
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==== Wrong logic
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`==` allows either of both operands to be `null`, while `equals()` doesn't.
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==== Readability and Understanding
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The `==` operator is a more concise and elegant way to test structural equality than calling a function.
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== How to fix it
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Replace `a.equals(b)` with `a == b`.
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=== Code examples
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==== Noncompliant code example
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[source,kotlin]
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----
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data class Person(
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val name: String,
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val firstName: String,
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val age: Int,
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val address: String
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)
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----
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[source,kotlin,diff-id=1,diff-type=noncompliant]
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----
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fun checkEquality() {
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val personA = Person("Claus", "Santa", 200, "North Pole")
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val personB = Person("Nicholas", "Saint", 1700, "Myra")
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personA.name.equals(personB.name) // Noncompliant, should use `==` instead
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personA.equals(personB) // Noncompliant, should use `==` instead
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}
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----
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==== Compliant solution
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[source,kotlin,diff-id=1,diff-type=compliant]
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----
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fun checkEquality() {
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val personA = Person("Claus", "Santa", 200, "North Pole")
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val personB = Person("Nicholas", "Saint", 1700, "Myra")
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personA.name == personB.name // Compliant
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personA == personB // Compliant
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}
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----
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== Resources
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=== Documentation
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* https://kotlinlang.org/docs/operator-overloading.html#equality-and-inequality-operators[Kotlin Docs, Equality and inequality operators]
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