Generic class declaration in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a generic class in Kotlin?

A generic class in Kotlin is a class that can work with any data type. It uses a placeholder type parameter, allowing the class to be flexible and reusable with different types.

beginner

How do you declare a generic class in Kotlin?

You declare a generic class by adding a type parameter inside angle brackets after the class name. For example: <br><code>class Box<T>(val value: T)</code> declares a generic class named Box with a type parameter T.

beginner

What does the type parameter <code>T</code> represent in <code>class Box<T></code>?

The type parameter <code>T</code> is a placeholder for any type that will be specified when creating an instance of the class. It allows the class to hold or work with values of that type.

beginner

Can you create an instance of a generic class with a specific type? Give an example.

Yes. For example, val intBox = Box<Int>(123) creates an instance of Box that holds an Int value 123. The type Int replaces the generic type parameter T.

beginner

Why use generic classes instead of regular classes?

Generic classes let you write code once and use it with many types. This avoids repeating similar classes for each type and helps keep code clean and flexible.

How do you declare a generic class named Container with a type parameter T in Kotlin?

A class Container<T>

B class Container(T)

C class Container<T>()

D class Container[]

The correct syntax for declaring a generic class uses angle brackets with the type parameter: class Container

What does the type parameter in a generic class represent?

A A fixed type like Int or String

B A variable name

C A function inside the class

D A placeholder for any type specified when creating an instance

The type parameter is a placeholder that gets replaced by a real type when you create an instance of the generic class.

Which of these is a valid way to create an instance of a generic class Box with type String?

A val box = Box<String>("hello")

B val box = Box(hello)

C val box = Box<String>

D val box = Box<String>(123)

You must specify the type and provide a value of that type. Box("hello") is correct.

Why are generic classes useful?

A They replace functions

B They make code slower

C They allow code reuse with different types

D They only work with Int types

Generic classes let you write flexible code that works with many types, avoiding repetition.

What symbol is used to declare a type parameter in a Kotlin generic class?

A [ ]

B < >

C ( )

D { }

Angle brackets < > are used to declare type parameters in Kotlin generic classes.

Explain how to declare a generic class in Kotlin and why it is useful.

Think about how you can write one class to work with many types.

Describe how you create an instance of a generic class with a specific type and give an example.

Remember to specify the type inside angle brackets when creating the object.