KOTLIN: Boolean
Sumber: https://www.tutorialspoint.com/kotlin/kotlin_booleans.htm
Many times we come across a situation where we need to take decision in Yes or No, or may be we can say True or False. To handle such situation Kotlin has a Boolean data type, which can take the values either true or false.
Kotlin also has a nullable counterpart Boolean? that can have the null value.
Create Boolean Variables
A boolean variable can be created using Boolean keyword and this variable can only take the values either true or false:
Example
fun main(args: Array<String>) {
val isSummer: Boolean = true
val isCold: Boolean = false
println(isSummer)
println(isCold)
}
When you run the above Kotlin program, it will generate the following output:
true false
In fact, we can create Kotlin boolean variables without using Boolean keyword and Kotlin will understand the variable type based on the assigned values either true or false
Kotlin Boolean Operators
Kotlin provides following built-in operators for boolean variables. These operators are also called Logical Operators:
Operator Name Description Example && Logical and Returns true if both operands are true x && y || Logical or Returns true if either of the operands is true x || y ! Logical not Reverse the result, returns false if the operand is true !x
Example
Following example shows different calculations using Kotlin Logical Operators:
fun main(args: Array<String>) {
var x: Boolean = true
var y:Boolean = false
println("x && y = " + (x && y))
println("x || y = " + (x || y))
println("!y = " + (!y))
}
When you run the above Kotlin program, it will generate the following output:
x && y = false x || y = true !y = true
Kotlin Boolean Expression
A Boolean expression returns either true or false value and majorly used in checking the condition with if...else expressions. A boolean expression makes use of relational operators, for example >, <, >= etc.
fun main(args: Array<String>) {
val x: Int = 40
val y: Int = 20
println("x > y = " + (x > y))
println("x < y = " + (x < y))
println("x >= y = " + (x >= y))
println("x <= y = " + (x <= y))
println("x == y = " + (x == y))
println("x != y = " + (x != y))
}
When you run the above Kotlin program, it will generate the following output:
x > y = true x < y = false x >= y = true x <= y = false x == y = false x != y = true
Kotlin and()and or() Functions
Kotlin provides and() and or() functions to perform logical AND and logical OR operations between two boolean operands.
These functions are different from && and || operators because these functions do not perform short-circuit evaluation but they always evaluate both the operands.
fun main(args: Array<String>) {
val x: Boolean = true
val y: Boolean = false
val z: Boolean = true
println("x.and(y) = " + x.and(y))
println("x.or(y) = " + x.or(y))
println("x.and(z) = " + x.and(z))
}
When you run the above Kotlin program, it will generate the following output:
x.and(y) = false x.or(y) = true x.and(z) = true
Kotlin also provides not() and xor() functions to perform Logical NOT and XOR operations respectively.
Boolean to String
You can use toString() function to convert a Boolean object into its equivalent string representation.
You will need this conversion when assigning a true or false value in a String variable.
fun main(args: Array<String>) {
val x: Boolean = true
var z: String
z = x.toString()
println("x.toString() = " + x.toString())
println("z = " + z)
}
When you run the above Kotlin program, it will generate the following output:
x.toString() = true z = true
Quiz Time (Interview & Exams Preparation)
Q 1 - Which of the following is true about Kotlin Boolean Data type?
A - Boolean data type can have two values true and false
B - Boolean data type can have two values 0 and 1
C - We can assign Boolean value to integer variable
D - All of the above
Q 2 - What will be the output of the following program:
fun main(args: Array<String>) {
val x: Boolean = true var y: String y = x
} A - This will compile successfully without error and warning
B - This will raise just a warning
C - Compilation will stop with error
D - None of the above