KOTLIN: Basic Syntax

Sumber: https://www.tutorialspoint.com/kotlin/kotlin_basic_syntax.htm

Kotlin Program Entry Point

An entry point of a Kotlin application is the main() function. A function can be defined as a block of code designed to perform a particular task.

Let's start with a basic Kotlin program to print "Hello, World!" on the standard output:

Titik masuk aplikasi Kotlin adalah fungsi main(). Fungsi dapat didefinisikan sebagai blok kode yang dirancang untuk melakukan tugas tertentu.

Mari kita mulai dengan program dasar Kotlin untuk mencetak "Halo, Dunia!" pada keluaran standar:

fun main() {
   var string: String  = "Hello, World!"
   println("$string")
}

When you run the above Kotlin program, it will generate the following output:

Ketika Anda menjalankan program Kotlin di atas, itu akan menghasilkan output berikut:

Hello, World!

Entry Point with Parameters

Another form of main() function accepts a variable number of String arguments as follows:

Bentuk lain dari fungsi main() menerima sejumlah variabel argumen String sebagai berikut:

fun main(args: Array<String>){
    println("Hello, world!")
}

When you run the above Kotlin program, it will generate the following output:

Ketika Anda menjalankan program Kotlin di atas, itu akan menghasilkan output berikut:

Hello, World!

If you have observed, its clear that both the programs generate same output, so it is very much optional to pass a parameter in main() function starting from Kotlin version 1.3.

Jika Anda telah mengamati, jelas bahwa kedua program menghasilkan output yang sama, jadi sangat opsional untuk melewatkan parameter dalam fungsi main() mulai dari Kotlin versi 1.3.

print() vs println()

The print() is a function in Kotlin which prints its argument to the standard output, similar way the println() is another function which prints its argument on the standard output but it also adds a line break in the output.

Let's try the following program to understand the difference between these two important functions:

print() adalah fungsi di Kotlin yang mencetak argumennya ke output standar, sama seperti println() adalah fungsi lain yang mencetak argumennya pada output standar tetapi juga menambahkan jeda baris pada output.

Mari kita coba program berikut untuk memahami perbedaan kedua fungsi penting ini:

fun main(args: Array<String>){
    println("Hello,")
    println(" world!")

    print("Hello,")
    print(" world!")
}

When you run the above Kotlin program, it will generate the following output:

Ketika Anda menjalankan program Kotlin di atas, itu akan menghasilkan output berikut:

Hello,
world!
Hello, world!

Both the functions (print() and println()) can be used to print numbers as well as strings and at the same time to perform any mathematical calculations as below:

Kedua fungsi (print() dan println()) dapat digunakan untuk mencetak angka serta string dan pada saat yang sama untuk melakukan perhitungan matematis seperti di bawah ini:

fun main(args: Array<String>){
    println( 200 )
    println( "200" )
    println( 2 + 2 ) 

    print(4*3)
}

When you run the above Kotlin program, it will generate the following output:

Ketika Anda menjalankan program Kotlin di atas, itu akan menghasilkan output berikut:

200
200
4
12

Semicolon (;) in Kotlin

Kotlin code statements do not require a semicolon (;) to end the statement like many other programming languages, such as Java, C++, C#, etc. do need it.

Though you can compile and run a Kotlin program with and without semicolon successfully as follows:

fun main() {
    println("I'm without semi-colon")
    
    println("I'm with semi-colon");
}

When you run the above Kotlin program, it will generate the following output:

I'm without semi-colon
I'm with semi-colon

So as a good programming practice, it is not recommended to add a semicolon in the end of a Kotlin statement.

Packages in Kotlin

Kotlin code is usually defined in packages though package specification is optional. If you don't specify a package in a source file, its content goes to the default package.

If we specify a package in Kotlin program then it is specified at the top of the file as follows:

package org.tutorialspoint.com

fun main() {
    println("Hello, World!")
}

When you run the above Kotlin program, it will generate the following output:

Hello, World!

Quiz Time (Interview & Exams Preparation)

Q 1 - Kotlin main() function should have a mandatory parameter to compile the code successfully:

A - True

B - False

Q 2 - What will be the output of the following Kotlin program

fun main() {

   println("1"); println("2")

} A - This will give a syntax error

B - It will print 12

C - 1 followed by 2 in the next line

D - None of the above

Q 3 - Which of the following statement is correct in Kotlin

A - A Kotlin program must have a main() function

B - A Kotlin program can be compiled without a main() function

C - It is mandatory to have a print() or println() functions in a Kotlin program

D - All statements are correct from Kotlin programming point of view

Referensi

• https://www.tutorialspoint.com/kotlin/kotlin_basic_syntax.htm