Example:
fun main(args: Array<String>) {
var a= 10 + 20
println(a)
}
Output:
30
Arithmetic Operators-算术运算符:
| Operators | Meaning | Expression | Translate to |
|---|---|---|---|
| + | Addition | a + b | a.plus(b) |
| - | Subtraction | a - b | a.minus(b) |
| * | Multiplication | a * b | a.times(b) |
| / | Division | a / b | a.div(b) |
| % | Modulus | a % b | a.rem(b) |
Example:
fun main(args: Array<String>)
{
var a = 20
var b = 4
println("a + b = " + (a + b))
println("a - b = " + (a - b))
println("a * b = " + (a.times(b)))
println("a / b = " + (a / b))
println("a % b = " + (a.rem(b)))
}
Output:
a + b = 24
a - b = 16
a * b = 80
a / b = 5
a % b = 0
Relational Operators-关系运算符
| Operators | Meaning | Expression | Translate to |
|---|---|---|---|
| > | greater than | a > b | a.compareTo(b) > 0 |
| < | less than | a < b | a.compareTo(b) < 0 |
| >= | greater than or equal to | a >= b | a.compareTo(b) >= 0 |
| <= | less than or equal to | a <= b | a.compareTo(b) <= 0 |
| == | is equal to | a == b | a?.equals(b) ?: (b === null) |
| != | not equal to | a != b | !(a?.equals(b) ?: (b === null)) > 0 |
Example:
fun main(args: Array<String>)
{
var c = 30
var d = 40
println("c > d = "+(c>d))
println("c < d = "+(c.compareTo(d) < 0))
println("c >= d = "+(c>=d))
println("c <= d = "+(c.compareTo(d) <= 0))
println("c == d = "+(c==d))
println("c != d = "+(!(c?.equals(d) ?: (d === null))))
}
Output:
c > d = false
c < d = true
c >= d = false
c <= d = true
c == d = false
c != d = true
Assignment Operators-赋值运算符
| Operators | Expression | Translate to |
|---|---|---|
| = | a = 5 | a.equalto(5) |
| += | a = a + b | a.plusAssign(b) > 0 |
| -= | a = a - b | a.minusAssign(b) < 0 |
| *= | a = a * b | a.timesAssign(b)>= 0 |
| /= | a = a / b | a.divAssign(b) <= 0 |
| %= | a = a % b | a.remAssign(b) |
Example:
fun main(args : Array<String>){
var a = 10
var b = 5
a+=b
println(a)
a-=b
println(a)
a*=b
println(a)
a/=b
println(a)
a%=b
println(a)
}
Output:
15
10
50
10
0
Unary Operators-单目运算符
| Operators | Expression | Translate to |
|---|---|---|
| ++ | ++a or a++ | a.inc() |
| – | –a or a– | a.dec() |
Example:
fun main(args : Array<String>){
var e=10
var flag = true
println("First print then increment: "+ e++)
println("First increment then print: "+ ++e)
println("First print then decrement: "+ e--)
println("First decrement then print: "+ --e)
}
Output:
First print then increment: 10
First increment then print: 12
First print then decrement: 12
First decrement then print: 10
Logical Operatorsz-逻辑运算符
| Operators | Meaning | Expression |
|---|---|---|
| && | Return true if all expressions are true | (a>b) && (a>c) |
| || | Return true if any of the expressions is true | (a>b) |
| ! | Return the complement of the expression | a.not() |
Example:
fun main(args : Array<String>){
var x = 100
var y = 25
var z = 10
var result = false
if(x > y && x > z)
println(x)
if(x < y || x > z)
println(y)
if( result.not())
println("Logical operators")
}
Output:
100
25
Logical operators
Bitwise Operators-位运算符
| Operators | Meaning | Expression |
|---|---|---|
| shl | signed shift left | a.shl(b) |
| shr | signed shift right | a.shr(b) |
| ushr | unsigned shift right | a.ushr() |
| and | bitwise and | a.and(b) |
| or | bitwise or | a.or() |
| xor | bitwise xor | a.xor() |
| inv | bitwise inverse | a.inv() |
Example:
fun main(args: Array<String>)
{
println("5 signed shift left by 1 bit: " + 5.shl(1))
println("10 signed shift right by 2 bits: : " + 10.shr(2))
println("12 unsigned shift right by 2 bits: " + 12.ushr(2))
println("36 bitwise and 22: " + 36.and(22))
println("36 bitwise or 22: " + 36.or(22))
println("36 bitwise xor 22: " + 36.xor(22))
println("14 bitwise inverse is: " + 14.inv())
}
Output:
5 signed shift left by 1 bit: 10
10 signed shift right by 2 bits: : 2
12 unsigned shift right by 2 bits: 3
36 bitwise and 22: 4
36 bitwise or 22: 54
36 bitwise xor 22: 50
14 bitwise inverse is: -15
Kotlin Output-Kotlin 输出
print() function // prints text
println() function // prints text and then moves the cursor to a new line
Example:
fun main(args: Array<String>)
{
print("Hello, Geeks! ")
println("This is Kotlin tutorial.")
print("By GFG!")
}
Output:
Hello, Geeks! This is Kotlin tutorial.
By GFG!
Print Literals and Variables-打印字面量和变量
Example:
fun sum(a: Int,b: Int) : Int{
return a + b
}
fun main(args: Array<String>){
var a = 10
var b = 20
var c = 30L
var marks = 40.4
println("Sum of {$a} and {$b} is : ${sum(a,b)}")
println("Long value is: $c")
println("marks")
println("$marks")
}
Output:
Sum of {10} and {20} is : 30
Long value is: 30
marks
40.4
Kotlin Input-Kotlin 输入
readline() method
Scanner class
Example:
fun main(args : Array<String>) {
print("Enter text: ")
var input = readLine()
print("You entered: $input")
}
Output:
Enter text: Hello, Geeks! You are learning how to take input using readline()
You entered: Hello, Geeks! You are learning how to take input using readline()
使用Scanner类从用户获取输入
Example:
import java.util.Scanner
fun main(args: Array<String>) {
// create an object for scanner class
val number1 = Scanner(System.`in`)
print("Enter an integer: ")
// nextInt() method is used to take
// next integer value and store in enteredNumber1 variable
var enteredNumber1:Int = number1.nextInt()
println("You entered: $enteredNumber1")
val number2 = Scanner(System.`in`)
print("Enter a float value: ")
// nextFloat() method is used to take next
// Float value and store in enteredNumber2 variable
var enteredNumber2:Float = number2.nextFloat()
println("You entered: $enteredNumber2")
val booleanValue = Scanner(System.`in`)
print("Enter a boolean: ")
// nextBoolean() method is used to take
// next boolean value and store in enteredBoolean variable
var enteredBoolean:Boolean = booleanValue.nextBoolean()
println("You entered: $enteredBoolean")
}
Output:
Enter an integer: 123
You entered: 123
Enter a float value: 40.45
You entered: 40.45
Enter a boolean: true
You entered: true
在不使用Scanner类的情况下从用户获取输入：
readline () ! !将输入作为字符串，并在后面加上（!!）以确保输入值不为空。
Example:
fun main(args: Array<String>) {
print("Enter an Integer value: ")
val string1 = readLine()!!
// .toInt() function converts the string into Integer
var integerValue: Int = string1.toInt()
println("You entered: $integerValue")
print("Enter a double value: ")
val string2= readLine()!!
// .toDouble() function converts the string into Double
var doubleValue: Double = string2.toDouble()
println("You entered: $doubleValue")
}
Output:
Enter an Integer value: 123
You entered: 123
Enter a double value: 22.22222
You entered: 22.22222
Kotlin Type Conversion- Kotlin类型转换
类型转换（也称为类型强制转换）是指将一种数据类型变量的实体更改为另一种数据类型。正如我们所知，Java支持从较小数据类型到较大数据类型的隐式类型转换。整数值可以分配给long数据类型。
但是，Kotlin不支持隐式类型转换。整数值不能分配给长数据类型。
Example:
public class TypecastingExample {
public static void main(String args[]) {
byte p = 12;
System.out.println("byte value : "+p);
// Implicit Typecasting
// integer value can be assigned
// to long data type
long q = p;
}
}
Output:
var myNumber = 100
var myLongNumber: Long = myNumber // Compiler error
// Initializer type mismatch: expected 'Long', actual 'Int'.
var myNumber = 100
var myLongNumber: Long = myNumber.toLong() // compiles successfully
下面的辅助函数可用于将一种数据类型转换为另一种数据类型：
toByte()
toShort()
toInt()
toLong()
toFloat()
toDouble()
toChar()
Example:
fun main(args: Array<String>)
{
println("259 to byte: " + (259.toByte()))
println("50000 to short: " + (50000.toShort()))
println("21474847499 to Int: " + (21474847499.toInt()))
println("10L to Int: " + (10L.toInt()))
println("22.54 to Int: " + (22.54.toInt()))
println("22 to float: " + (22.toFloat()))
println("65 to char: " + (65.toChar()))
// Char to Number is deprecated in kotlin
println("A to Int: " + ('A'.toInt()))
}
Output:
259 to byte: 3
50000 to short: -15536
21474847499 to Int: 11019
10L to Int: 10
22.54 to Int: 22
22 to float: 22.0
65 to char: A
A to Int: 65