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:
fun main() {
var string: String = "Hello, World!"
println("$string")
}
When you run the above Kotlin program, it will generate the following output:
Hello, World!
Entry Point with Parameters
Another form of main() function accepts a variable number of String arguments as follows:
fun main(args: Array<String>){
println("Hello, world!")
}
When you run the above Kotlin program, it will generate the following output:
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.
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:
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:
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:
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:
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