1. Introduction
In Kotlin, understanding the difference between class and object is crucial for proper object-oriented programming. A class in Kotlin is a blueprint for creating objects. It can contain properties, methods, and constructors. An object, on the other hand, is a singleton instance of a class. The object declaration in Kotlin combines class declaration and its single instance creation into one concise statement.
2. Key Points
1. Instances: A class can have multiple instances, an object is a single instance.
2. Declaration: Classes are declared using the class keyword, and objects are declared using the object keyword.
3. Initialization: Objects are initialized when they are first accessed, and classes are initialized when instantiated.
4. Use Case: Objects are used for singletons and utility functions, and classes are used for creating multiple objects with similar properties and behaviors.
3. Differences
Characteristic | Class | Object |
---|---|---|
Instances | Multiple instances | Single instance (Singleton) |
Declaration | class keyword | object keyword |
Initialization | When instantiated | When first accessed |
Use Case | Creating multiple objects | Singletons, utility functions |
4. Example
// Example of a Class
class MyClass {
var name: String = "MyClass"
fun showName() {
println(name)
}
}
// Example of an Object
object MyObject {
var name: String = "MyObject"
fun showName() {
println(name)
}
}
Output:
Class Output: Creating an instance of MyClass and calling showName will print "MyClass" Object Output: Calling showName on MyObject will print "MyObject"
Explanation:
1. MyClass can be instantiated multiple times, each instance having its own name property.
2. MyObject is a single instance, and its name property is shared across the entire application.
5. When to use?
- Use class when you need to create multiple instances, each with their own state.
- Use object for singletons where only a single instance should exist, or for utility functions that do not require multiple instances.
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