Why does this Kotlin method have enclosing backtic

Question

What are the backticks used for in the snippet below?

Why add them around the fun is(amount:Int ):Boolean { ... }?

verifier.`is`(amount)

Answer 1

It allows you to call a Java method whose name is a Kotlin keyword. It won't work if you leave out the backticks.

Answer 2

The backtick are a "workaround" to allow you to call methods that have a name representing a Kotlin keyword.

See kotlinlang:

Some of the Kotlin keywords are valid identifiers in Java: in, object, is, etc. If a Java library uses a Kotlin keyword for a method, you can still call the method escaping it with the backtick (`) character

Answer 3

It's because is is a reserved keyword in Kotlin. Since Kotlin is supposed to be interoperable with Java and is is a valid method (identifier) name in Java, the backticks are used to escape the method so that it can be used as a method without confusing it as a keyword. Without it it will not work because it would be invalid syntax.

This is highlighted in the Kotlin documentation:

Escaping for Java identifiers that are keywords in Kotlin

Some of the Kotlin keywords are valid identifiers in Java: in, object, is, etc. If a Java library uses a Kotlin keyword for a method, you can still call the method escaping it with the backtick (`) character

foo.`is`(bar)

Answer 4

is in list of Kotlin reserved words To use Kotlin reserved word (such as is or object) for function/class name you should wrap it to backticks

Answer 5

Some of the Kotlin keywords are valid identifiers in Java: in, object, is, etc. If a Java library uses a Kotlin keyword for a method, you can still call the method escaping it with the backtick (`) character

https://kotlinlang.org/docs/reference/java-interop.html