Kotlin print to console

Basic syntax

This is a collection of basic syntax elements with examples. At the end of every section, you’ll find a link to a detailed description of the related topic.

You can also learn all the Kotlin essentials with the free Kotlin Core track by JetBrains Academy.

Package definition and imports

Package specification should be at the top of the source file.

It is not required to match directories and packages: source files can be placed arbitrarily in the file system.

Program entry point

An entry point of a Kotlin application is the main function.

Another form of main accepts a variable number of String arguments.

Print to the standard output

print prints its argument to the standard output.

println prints its arguments and adds a line break, so that the next thing you print appears on the next line.

Functions

A function with two Int parameters and Int return type.

A function body can be an expression. Its return type is inferred.

A function that returns no meaningful value.

Unit return type can be omitted.

Variables

Read-only local variables are defined using the keyword val . They can be assigned a value only once.

Variables that can be reassigned use the var keyword.

You can declare variables at the top level.

Creating classes and instances

To define a class, use the class keyword.

Properties of a class can be listed in its declaration or body.

The default constructor with parameters listed in the class declaration is available automatically.

Inheritance between classes is declared by a colon ( : ). Classes are final by default; to make a class inheritable, mark it as open .

Comments

Just like most modern languages, Kotlin supports single-line (or end-of-line) and multi-line (block) comments.

Block comments in Kotlin can be nested.

See Documenting Kotlin Code for information on the documentation comment syntax.

String templates

Conditional expressions

In Kotlin, if can also be used as an expression.

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Kotlin Input and Output Using Console

In this tutorial you will learn how to take input and print output on console in Kotlin.

Kotlin Print Output on Console

Kotlin provides print() and println() functions for printing something on console. As kotlin language is derived from Java so these two functions internally call java methods System.out.print() and System.out.println().

There is a little difference between print() and println() in kotlin. The print() function doesn’t adds a new line after printing the statement while println() adds new line. You can see in above program output, the World is printed just after Hello. While the value of num variable is printed in a new line.

For printing the value of variable on console we simply add $ sign before variable name in the print statement. You can see this in above example.

Kotlin Take Input from Console

For taking input from user in kotlin we have a function readLine(). This function reads a line from console and by default the value that is read is string type.

enter your name:neeraj
hello neeraj

How to Read Integer in Kotlin?

In above program we read a string type value. What if you want to read other type of value? Let say you want to read integer value from console in kotlin, it can be done in following way.

enter a number:20
you entered 20

In above program we converted string input to integer using toInt() function. You can use toFloat(), toLong(), etc to convert to any other type also.

You can ask your queries in the comment section below.

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Kotlin Print to Console in Android Studio

1. What is the Logcat Window
2. Kotlin Print to Console in Android Studio

The console is the system’s monitor connected with an input device. We must display messages on the console to understand what the compiler is doing in the backend.

Suppose an error occurs while executing a code. How will we know what error has occurred unless we see it on the console?

Hence, printing to the console is of utmost importance.

There are different ways in different languages to print to console. We use printf() in C, cout in C++, System.out.println() in Java and println() in Kotlin.

But the Android Studio works a little differently. Using println() in the Android Studio won’t display any message on the console in Kotlin.

So how can we print to console using Kotlin in Android Studio? This article will give you an answer for just that.

What is the Logcat Window

Before moving into how to print to console using Kotlin in Android Studio, we need to understand the Logcat Window. Well, Logcat Window is the Android Studio’s console.

Any message we print to the console is displayed on the Logcat Window.

Kotlin Print to Console in Android Studio

We can print to console using Kotlin in Android Studio with the help of the log class. It is a predefined class that allows writing messages to the console.

We must import the log class’ library android.util.Log to print to the console using Kotlin.

Here’s the basic syntax to print to console.

import android.util.Log  ...>  Log.d("TAG", "message")  ...> 

1. v ( Verbose )
2. d ( Debug )
3. i ( Information )
4. w ( Warning )
5. e ( Error )
6. a ( Assert )

As we can see in the syntax, the log class takes two arguments: «TAG» and «message» .

In the place of the «TAG» , we need to write an indicator for the console command. And for the «message» , we need to write a message we want to print on the console.

Kailash Vaviya is a freelance writer who started writing in 2019 and has never stopped since then as he fell in love with it. He has a soft corner for technology and likes to read, learn, and write about it. His content is focused on providing information to help build a brand presence and gain engagement.

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Mastering Kotlin Android: A Complete Guide to Print to Console

Learn how to print output to the console in Kotlin Android. Discover the best practices, common issues, and unit testing for debugging and testing. Get started now with our comprehensive guide.

Mastering Kotlin Android: A Complete Guide to Print to Console

Kotlin and Android Studio are commonly used for Android development. Printing output to the console is a useful tool for debugging and testing. This guide will show you how to print output to the console in Kotlin Android.

Subheading 1: Using the Log class

The Log class is a part of the Android SDK and has various methods for printing different types of logs like debug, info, warning, and error. To print output on the console in Android Studio using the Log class, create a new project or open an existing project, then write log messages in the onCreate method of the activity’s Java or Kotlin file. The Logcat is the console in Android Studio where you can view the logs. The Logcat has filters to reduce the amount of logs shown.

Here is an example of how to use the Log class to print a debug log message to the console:

Subheading 2: print() and println() functions

There are also print() and println() functions in Kotlin for printing to the console. The print() function calls Java’s System.out.println() method internally. The dollar symbol ($) can be used to print variables inside a print statement. The Kotlin print() and println() methods won’t work in Flutter.

Here is an example of how to use the print() function to print a string and a variable to the console:

val myString = "Hello, world!" val myNumber = 42print("$myString $myNumber") 

Subheading 3: Unit testing console output

You can test console output using unit testing in Kotlin. This involves creating a test class and writing test methods to check that the console output is correct. The Console class has a format() method for writing formatted strings to the console.

Here is an example of how to use unit testing to test console output:

import org.junit.Test import org.junit.Assert.*class MyUnitTest < @Test fun consoleOutputTest() < val myString = "Hello, world!" val myNumber = 42 val expectedOutput = "$myString $myNumber" val outputStream = ByteArrayOutputStream() val printStream = PrintStream(outputStream) System.setOut(printStream) Console.format("%s %d", myString, myNumber) val actualOutput = outputStream.toString().trim() assertEquals(expectedOutput, actualOutput) >> 

Subheading 4: printStackTrace() method

The printStackTrace() method can be used to print detailed descriptions of throwables. This is useful for debugging and troubleshooting errors.

Here is an example of how to use the printStackTrace() method to print a detailed description of an exception to the console:

Subheading 5: Best practices and common issues

Best practices for printing to the console include using clear and descriptive log messages, avoiding excessive logging, and using filters to reduce noise. Common issues with printing to the console include accidentally logging sensitive information, logging too much information, and not logging enough information for debugging purposes. Debugging and testing are important parts of the software development process.

Printing output to the console is a useful tool for debugging and testing. The Log class and its various methods like Log.d() can be used to print to the console in Android Studio using Kotlin. The print() and println() functions are also available in Kotlin. Unit testing can be used to test console output, and the printStackTrace() method is useful for troubleshooting errors. Best practices include using clear and descriptive log messages, avoiding excessive logging, and using filters to reduce noise.

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