Kotlin val and var, types, string templates, nullable types, safe calls, the elvis operator, when and control flow.
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- What is the difference between val and var in Kotlin?
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val is immutable (read-only), var is mutable (can be reassigned)- Does Kotlin require explicit type declarations for variables?
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No, Kotlin can infer types from the assigned value, though explicit types are allowed- What is the default integer type in Kotlin?
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Int, which is a 32-bit signed integer- How do you declare a String variable in Kotlin?
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Use the String type, e.g., val name: String = "Alice", or let the compiler infer it- What values can a Boolean variable hold in Kotlin?
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Only true or false- What is the syntax for inserting a variable inside a string template?
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Use $variableName, e.g., "Hello $name"- How do you evaluate an expression inside a string template?
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Wrap it in curly braces: ${expression}, e.g., "The answer is ${2 + 2}"- How do you print a literal dollar sign in a string template?
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Use a backslash to escape it: \$, e.g., "Cost is \$100"- How do you declare a variable that can hold null in Kotlin?
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Add a question mark after the type: Type?, e.g., val x: Int? = null- What is the default for a variable type in Kotlin if no question mark is added?
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Non-nullable, meaning it cannot hold null and must be initialized with a value- Why does Kotlin require explicit nullable types?
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To prevent null pointer exceptions by making nullability explicit and forcing you to handle null cases- What is the syntax for the safe call operator in Kotlin?
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?. (question mark followed by a dot), e.g., obj?.method()- What does the safe call operator do when the object is null?
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It returns null instead of throwing a null pointer exception- What happens when you use ?. on an object that is not null?
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The method or property is called normally and the result is returned- What is the symbol for the elvis operator in Kotlin?
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?: (question mark followed by colon)
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