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  4. Cascade 'if' can be replaced with 'when'

Cascade 'if' can be replaced with 'when'

Last modified: 03 December 2024

Reports if statements with three or more branches that can be replaced with the when expression.

Example:

fun checkIdentifier(id: String) {
    fun Char.isIdentifierStart() = this in 'A'..'z'
    fun Char.isIdentifierPart() = isIdentifierStart() || this in '0'..'9'

    if (id.isEmpty()) {
        print("Identifier is empty")
    } else if (!id.first().isIdentifierStart()) {
        print("Identifier should start with a letter")
    } else if (!id.subSequence(1, id.length).all(Char::isIdentifierPart)) {
        print("Identifier should contain only letters and numbers")
    }
}

The quick-fix converts the if expression to when:

fun checkIdentifier(id: String) {
    fun Char.isIdentifierStart() = this in 'A'..'z'
    fun Char.isIdentifierPart() = isIdentifierStart() || this in '0'..'9'

    when {
        id.isEmpty() -> {
            print("Identifier is empty")
        }
        !id.first().isIdentifierStart() -> {
            print("Identifier should start with a letter")
        }
        !id.subSequence(1, id.length).all(Char::isIdentifierPart) -> {
            print("Identifier should contain only letters and numbers")
        }
    }
}

Locating this inspection

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CascadeIf
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Inspection Details

By default bundled with:

IntelliJ IDEA 2024.3, Qodana for JVM 2024.3,

Can be installed with plugin:

Kotlin, 243.23126-IJ