Kotlin Input/Output

Kotlin standard input output operations are performed to flow byte stream from input device (keyboard) to main memory and from main memory to output device (screen).

Kotlin Output

Kotlin output operation is performed using the standard methods print() and println(). Let's see an example:

fun main(args: Array< String>) {  
    println("Hello World!")  
    print("Welcome to  JavaTpoint")  
}  
fun main(args: Array< String>) {  
    println("Hello World!")  
    print("Welcome to  JavaTpoint")  
}  			  

Hello World!
Welcome to  MCA TUTORIALS

The methods print() and println() are internally call System.out.print() and System.out.println() respectively.

Difference between print() and println() methods:

• print(): print() method is used to print values provided inside the method "()".
• println(): println() method is used to print values provided inside the method "()" and moves cursor to the beginning of next line.

fun main(args: Array< String>){  
    println(10)  
    println("Welcome to  JavaTpoint")  
    print(20)  
    print("Hello")  
}  
fun main(args: Array< String>){  
    println(10)  
    println("Welcome to  JavaTpoint")  
    print(20)  
    print("Hello")  
}  

10
Welcome to  MCA Tutorials
20Hello

Kotlin Input

Kotlin has standard library function readLine() which is used for reads line of string input from standard input stream. It returns the line read or null. Let's see an example:

fun main(args: Array< String>) {  
    println("Enter your name")  
    val name = readLine()  
    println("Enter your age")  
    var age: Int =Integer.valueOf(readLine())  
    println("Your name is $name and your age is $age")  
}  
fun main(args: Array< String>) {  
    println("Enter your name")  
    val name = readLine()  
    println("Enter your age")  
    var age: Int =Integer.valueOf(readLine())  
    println("Your name is $name and your age is $age")  
}  

Enter your name
Ashutosh
Enter your age
25
Your name is Ashutosh and your age is 25

While using the readLine() function, input lines other than String are explicitly converted into their corresponding types.
To input other data type rather than String, we need to use Scanner object of java.util.Scanner class from Java standard library.

import java.util.Scanner  
fun main(args: Array< String>) {  
    val read = Scanner(System.`in`)  
    println("Enter your age")  
    var age = read.nextInt()  
    println("Your input age is "+age)  
}  
import java.util.Scanner  
fun main(args: Array< String>) {  
    val read = Scanner(System.`in`)  
    println("Enter your age")  
    var age = read.nextInt()  
    println("Your input age is "+age)  
}  

Enter your age
25
Your input age is 25

Here nextInt() is a method which takes integer input and stores in integer variable. The other data types Boolean, Float, Long and Double uses nextBoolean(), nextFloat(), nextLong() and nextDouble() to get input from user.