Kotlin - Operators
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An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Kotlin is rich in built-in operators and provide the following types of operators:

  • Arithmetic Operators

  • Relational Operators

  • Assignment Operators

  • Unary Operators

  • Logical Operators

  • Bitwise Operations

Now let's look into these Kotlin Operators one by one.

(a) Kotlin Arithmetic Operators

Kotlin arithmetic operators are used to perform basic mathematical operations such as addition, subtraction, multiplication and division etc.

Operator Name Description Example
+ Addition Adds together two values x + y
- Subtraction Subtracts one value from another x - y
* Multiplication Multiplies two values x * y
/ Division Divides one value by another x / y
% Modulus Returns the division remainder x % y

Example

Following example shows different calculations using Kotlin Arithmetic Operators:

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))
}

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

x + y = 60
x - y = 20
x / y = 2
x * y = 800
x % y = 0

(b) Kotlin Relational Operators

Kotlin relational (comparison) operators are used to compare two values, and returns a Boolean value: either true or false.

Operator Name Example
> greater than x > y
< less than x < y
>= greater than or equal to x >= y
<= less than or equal to x <= y
== is equal to x == y
!= not equal to x != y

Example

Following example shows different calculations using Kotlin Relational Operators:

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

(c) Kotlin Assignment Operators

Kotlin assignment operators are used to assign values to variables.

Following is an example where we used assignment operator = to assign a values into two variables:

fun main(args: Array<String>) {
   val x: Int = 40
   val y: Int = 20
   
   println("x = " +  x)
   println("y = " +  y)
}

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

x = 40
y = 20

Following is one more example where we used assignment operator += to add the value of self variable and assign it back into the same variable:

fun main(args: Array<String>) {
   var x: Int = 40

   x += 10
      
   println("x = " +  x)
}

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

x = 50

Following is a list of all assignment operators:

Operator Example Expanded Form
= x = 10 x = 10
+= x += 10 x = x - 10
-= x -= 10 x = x - 10
*= x *= 10 x = x * 10
/= x /= 10 x = x / 10
%= x %= 10 x = x % 10

Example

Following example shows different calculations using Kotlin Assignment Operators:

fun main(args: Array<String>) {
   var x: Int = 40

   x += 5
   println("x += 5 = " + x )
   
   x = 40;
   x -= 5
   println("x -= 5 = " +  x)
   
   x = 40
   x *= 5
   println("x *= 5 = " +  x)
   
   x = 40
   x /= 5
   println("x /= 5 = " +  x)
   
   x = 43
   x %= 5
   println("x %= 5 = " + x)
}

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

x += 5 = 45
x -= 5 = 35
x *= 5 = 200
x /= 5 = 8
x %= 5 = 3

(d) Kotlin Unary Operators

The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.

Following is the list of Kotlin Unary Operators:

Operator Name Example
+ unary plus +x
- unary minus -x
++ increment by 1 ++x
-- decrement by 1 --x
! inverts the value of a boolean !x

Example

Following example shows different calculations using Kotlin Unary Operators:

fun main(args: Array<String>) {
   var x: Int = 40
   var b:Boolean = true

   println("+x = " +  (+x))
   println("-x = " +  (-x))
   println("++x = " +  (++x))
   println("--x = " +  (--x))
   println("!b = " +  (!b))
}

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

+x = 40
-x = -40
++x = 41
--x = 40
!b = false

Here increment (++) and decrement (--) operators can be used as prefix as ++x or --x as well as suffix as x++ or x--. The only difference between the two forms is that in case we use them as prefix then operator will apply before expression is executed, but if use them as suffix then operator will apply after the expression is executed.

(e) Kotlin Logical Operators

Kotlin logical operators are used to determine the logic between two variables or values:

Following is the list of Kotlin 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

(e) Kotlin Bitwise Operations

Kotlin does not have any bitwise operators but Kotlin provides a list of helper functions to perform bitwise operations.

Following is the list of Kotlin Bitwise Functions:

Function Description Example
shl (bits) signed shift left x.shl(y)
shr (bits) signed shift right x.shr(y)
ushr (bits) unsigned shift right x.ushr(y)
and (bits) bitwise and x.and(y)
or (bits) bitwise or x.or(y)
xor (bits) bitwise xor x.xor(y)
inv() bitwise inverse x.inv()

Example

Following example shows different calculations using Kotlin bitwise functions:

fun main(args: Array<String>) {
   var x:Int = 60	  // 60 = 0011 1100  
   var y:Int = 13	  // 13 = 0000 1101
   var z:Int

   z = x.shl(2)       // 240 = 1111 0000
   println("x.shl(2) = " +  z)
   
   z = x.shr(2)       // 15 = 0000 1111
   println("x.shr(2) = " +  z)
   
   z = x.and(y)       // 12 = 0000 1100
   println("x.and(y)  = " +  z)
   
   z = x.or(y)        // 61 = 0011 1101
   println("x.or(y)  = " +  z)
   
   z = x.xor(y)       // 49 = 0011 0001
   println("x.xor(y)  = " +  z)
   
   z = x.inv()        // -61 = 1100 0011
   println("x.inv()  = " +  z)
}

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

x.shl(2) = 240
x.shr(2) = 15
x.and(y)  = 12
x.or(y)  = 61
x.xor(y)  = 49
x.inv()  = -61

Quiz Time (Interview & Exams Preparation)

Answer : D

Explanation

Given operator % is called Arithmetic Modulus operator and returns the remainder after dividing one number by another number.

Q 2 - Kotlin supports a good number of bitwise operators

A - Correct

B - Incorrect

Answer : B

Explanation

This is incorrect statement because Kotlin does not provide any Bitwise operators, rather it provides a set of function to perform bitwise operations.

Answer : C

Explanation

Given operator ++ is called unary increment operator in Kotlin

Q 4 - Which of the following function will do bitwise right shift operation?

A - x.ushr(y)

B - x.shr(y)

C - x.shl(y)

D - None of the above

Answer : B

Explanation

Function x.shr(y) is used to shift the bits towards right by y times for a given x operand.

Q 5 - Which of the following is a logical inverse operator:

A - inv()

B - !

C - &&

D - ||

Answer : B

Explanation

Yes operator ! is used to inverse the value of an operand.

Q 6 - What will be the output of the following Kotlin code:

fun main(args: Array<String>) {
   var x: Int = 40

   x += 10

   println(x)
}

A - 40

B - Syntax Error

C - 50

D None of the above

Answer : C

Explanation

Here given operator += is addition assignment operator which mean it will be equvivalent to x = x + 10 which will yield a value of 50.

Q 7 - What will be the output of the following Kotlin code:

fun main(args: Array<String>) {
   var x: Int = 60

   println(x.shr(2))
}

A - 15

B - Syntax Error

C - 50

D None of the above

Answer : C

Explanation

Correct value is 15 because x.shr(2) will shift x value by two places. So it x value is 60 = 0011 1100 , then after doing right shift it will give us 15 which is 0000 1111

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