Hello World program in Kotlin

Hello, World! is the first basic program in any programming language. Let’s write the first program in Kotlin programming language.

The “Hello, World!” program in Kotlin –

Open your favorite editor notepad or notepad++ and create a file named firstapp.kt with the following code.

// Kotlin Hello World Program
fun main(args: Array<String>) {
    println("Hello, World!")
}

You can compile the program in command line compiler.

$ kotlinc firstapp.kt

Now Run the program to see the output in command line compiler.

$kotlin firstapp.kt
Hello, World!

You can run the program in Intellij IDEA as shown in Setting up the environment article.

Details about the “Hello, World!” program –

Line #1:
First line is a comment which is ignored by the compiler. Comments are added in program with the purpose of making the source code easier for readers to understand.

Kotlin supports two type of comments –

  1. Single line comment
                   // single line comment
    
  2. Mulitple line comment
                  /*   This is 
                       multi line 
                       comment 
                 */
    

Line #2:
The second line defines the main function

 fun main(args: Array<String>) {
    // ...
}

The main() function is the entry point of every program. All functions in kotlin start fun keyword followed by the name of function(here main is the name), a list of parameters, an optional return type and the body of the function ( { ……. } ).
In this case, main function contains the argument – an array of strings and return units. Unit type corresponds to void in java means the function does not return any value.

Line #3:
The third line is a statement and it prints “Hello, World!” to standard output of the program.

println("Hello, World!")

Semicolons are optional in Kotlin, like other modern programming languages.



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