Kotlin Class: Logger class with companion object for logging

Last update on February 05 2025 05:41:32 (UTC/GMT +8 hours)

Write a Kotlin program that creates a class 'Logger' with a companion object that provides logging functionality.

Pre-Knowledge (Before You Start!)

Before attempting this exercise, you should be familiar with the following concepts:

• Classes and Objects: Understanding how to define and use classes in Kotlin.
• Companion Objects: Special objects in Kotlin that allow you to define static-like methods inside a class.
• Private Constructors: Preventing direct instantiation of a class to enforce controlled access.
• Singleton Pattern: Using a companion object to ensure only one instance of logging functionality is used.
• Printing to Console: Using println() to display messages.

Hints (Try Before Looking at the Solution!)

Try to solve the problem using these hints:

• Hint 1: Define a class named Logger with a private constructor to prevent object creation.
• Hint 2: Inside the Logger class, define a companion object.
• Hint 3: Add a function inside the companion object to log messages.
• Hint 4: Use println() to display the log message in a formatted way.
• Hint 5: In the main() function, call the log function using Logger.log("message").

Sample Solution:

Kotlin Code:

class Logger private constructor() {
    companion object {
        fun log(message: String) {
            println("Logging: $message")
        }
    }
}

fun main() {
    Logger.log("This is a log message.")
}

Sample Output:

Logging: This is a log message

Explanation:

In the above exercise -

• First we define a "Logger" class with a private constructor to prevent direct instantiation of the class. Inside the "Logger" class, we have a companion object that provides logging functionality.
• The companion object contains a log function that takes a message parameter and prints a log message. In this example, it simply prints the message with "Logging: ".
• In the "main()" function, we call the log function of the Logger class through the companion object by using the syntax Logger.log("message"). This logs the provided message.

Kotlin Editor:

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